Concentration dependent spectroscopic behavior of Sm3+ doped leadfluoro-borophosphate glasses for laser and LED applications

Accepted Manuscript 3+ Concentration dependent Spectroscopic behaviour of Sm doped Leadfluoroborophosphate glasses for Laser and LED applications M. Vijayakumar, K. Marimuthu, V. Sudarsan PII:

S0925-8388(15)30182-1

DOI:

10.1016/j.jallcom.2015.06.064

Reference:

JALCOM 34406

To appear in:

Journal of Alloys and Compounds

Received Date: 15 April 2015 Revised Date:

4 June 2015

Accepted Date: 7 June 2015

Please cite this article as: M. Vijayakumar, K. Marimuthu, V. Sudarsan, Concentration dependent 3+ Spectroscopic behaviour of Sm doped Leadfluoro-borophosphate glasses for Laser and LED applications, Journal of Alloys and Compounds (2015), doi: 10.1016/j.jallcom.2015.06.064. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT 3+

3+

28

Non-radiative phonon relaxation 4

20

6 F 6 11/2 F 6 9/2 F 6 7/2 F 5/2

CR1 CR2 CR3 CR4

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12

402 nm

16

562 nm 598 nm 644 nm 707 nm

G 5/2

8

0

Emission

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Excitation

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4

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3 -1 Energy (×10 cm )

24

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4 D 4 7/2 D 6 3/2 P 6 7/2 P 6 3/2 P 4 5/2 G 4 9/2 I 4 13/2 I 11/2

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Sm ion

Sm ion

6 H 6 11/2 H 6 9/2 H 6 7/2 H 5/2

Cross relaxation

4 G 5/2

6 F 6 11/2 F 6 9/2 F 6 7/2 F 5/2 6 H 6 11/2 H 6 9/2 H 6 7/2 H 5/2

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Concentration dependent Spectroscopic behaviour of Sm3+ doped Leadfluoro-borophosphate glasses for Laser and LED applications M.Vijayakumar1, K.Marimuthu1,*, V.Sudarsan2 1

Department of Physics, Gandhigram Rural University, Gandhigram - 624 302, India

Radio Chemistry Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India

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2

Abstract

A new series of Sm3+ doped leadfluoro-borophosphate glasses with the composition

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50B2O3+(20−x)P2O5+10Li2O+10ZnF2+10PbO+xSm2O3 (where x = 0, 0.05, 0.1, 0.25, 0.5, 1 and 2 in wt%) were prepared by following the melt quenching technique and their structural

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and spectroscopic behavior were studied through XRD, FTIR, optical absorption, luminescence and decay measurements. The presence of fundamental vibrational groups such as BO3, BO4 and PO4 were explored through the FTIR spectral measurements and further increasing BO4 units with NBO were also found out. The nephelauxetic effect and Judd-Ofelt (JO) theory have been applied to investigate the nature of the Sm–O bond and the local environment around the Sm3+ ion site. The luminescence intensity decreases with the increase

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in Sm3+ ion concentration beyond 0.5 wt% and the same was discussed through various energy transfer mechanism which takes place between Sm3+ ions. The lasing parameters like stimulated emission cross-section (σ ), branching ratios (βR) and radiative lifetime (τcal) for the 4G5/2→6H5/2, 4G5/2→6H7/2, 4G5/2→6H9/2 and 4G5/2→6H11/2 emission transitions have been

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calculated, discussed and reported. The R/O intensity ratios have been studied by varying the RE ion concentration and further CIE colour chromaticity coordinates have also been

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calculated to characterize the emission of the prepared glasses. The color purity and the correlated color temperature were also calculated and the results were discussed in the present work. The decay of the 4G5/2 excited level is found to be single exponential upto 0.1 wt% and after that it changes into non-exponential for higher concentration and the nonexponential behavior arises due to the energy transfer between the Sm3+ ions through various cross-relaxation channels and the decay of the 4G5/2 excited level have been analyzed with IH model. Among the prepared glasses, BPLP0.5S glass exhibits higher  , βR,  × and  ×∆λeff values corresponding to the 4G5/2→6H7/2 emission band and these are in turn specifies its suitability for LEDs and visible laser applications.

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ACCEPTED MANUSCRIPT Keyword: Nephelauxetic effect, Judd-Ofelt theory, Stimulated emission cross-section, R/O intensity ratio, IH model. *

Corresponding author. Tel.: +91 451 2452371; Fax: +91 451 2454466.

E-mail address: [email protected] 1. Introduction

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In recent years, researchers were motivated towards RE3+ doped materials due to their fascinating applications in various technologies such as sensors, luminescence materials and opto-electronic devices as temperature sensors, solid state lighting (SSL) systems, solar energy collectors, energy convertors, Q-switching devices, high power laser gain medium,

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upconvertors, under sea optical communications, optical data storage devices and also in Xray imaging technology [1−6]. The electronic energy levels of the RE ions determine the lasing characteristics, radiative properties which are influenced by the local perturbation

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around the RE ions and because of these reasons RE ions were doped into different host matrices which exhibit different lasers and luminescence properties [7,8]. Over the past few decades, lot of active research was focused on the rare earth doped glasses based on concentration and host dependent spectroscopic properties through optical absorption and luminescence spectral measurements to examine their suitability for various photonic

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applications. The doping of rare earth ions into glasses possess more advantages like large RE ion doping capability, possibility of tuning the intensity of emission band (hypersensitive transitions), broad inhomogeneous band width, low production cost, less preparation time and easy to fabricate into different shapes compared to the crystalline materials [9].

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Among the glass formers, phosphate (P2O5) based glasses possess interesting properties like lower phonon energy, high optical quality, low melting temperature, relatively

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high density, large emission cross-section and narrow emission bandwidth [9] but it has limitations like poor mechanical strength, low thermal stability, low chemical durability, larger thermal expansion coefficient and lower fracture toughness which limits the applications of phosphate glasses as a host material for high power lasers [10]. The addition of Borate (B2O3) groups into phosphate glasses deserves increasing interest in practical applications and make them potential candidate for various photonic applications [11] and the boro-phosphate glasses possess combined advantages of both the borate and phosphate glasses such as good optical quality, good thermal and mechanical stability, good rare earth ion solubility, large emission cross-section and narrow emission bandwidth [9]. Addition of heavy metal oxides (HMO) such as PbO modify the P‒O‒P and P‒O‒B bonds with the

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ACCEPTED MANUSCRIPT formation of M–O–P bonds [9] and further PbO posses dual bonding nature with the network formers such as Pb−O bond is ionic when PbO6 structural units were seen in the glass network and Pb−O bond is covalent when PbO4 units were formed [1]. It leads to enhance the mechanical strength, thermal stability, chemical durability and reduces the glass transition temperature of the boro-phosphate glasses and further enhance the radiative transition rates of

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the RE ions [1]. The phonon energy of the boro-phosphate glasses were reduced by adding ZnF2 which further reduces the non-radiative decay and water absorbance properties of the glass as a consequence the luminescence quenching caused by the OH− content have been reduced hence it helps to increase the luminescence yield of the RE ions [12].

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Among the RE3+ ions, Sm3+ ion is an important optical activator which exhibit strong orange-red luminescence in the visible region which is useful in high density optical storage, under sea communication, color displays and visible solid-state lasers [13]. The Sm3+ ion

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possess promising characteristics for spectral hole burning studies and is suitable to analyse and understand the energy transfer between RE3+−RE3+ ions or RE3+ ions and host matrix through various relaxation process [14]. The Sm3+ ions exhibit four dominant emission bands in the visible spectrum such as 4G5/2 → 6H5/2 , 6H7/2

,

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H9/2 and 6H11/2 from its lower emitting

meta stable state (4G5/2) with higher quantum efficiency [13]. Among the emission bands, G5/2 → 6H9/2 emission is due to electric dipole allowed transition and this transition is highly

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influenced by the host matrix and the intensity of the transition can be modified by the ligand field around the RE-ion site [15].

Ramachari et al. [15] investigated structural and luminescence behaviour of Sm3+ ions

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in oxyfluorosilicate glasses for the optical amplifier and LED applications and also reported the lifetime quenching at higher concentrations due to the energy transfer between Sm3+ ions.

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Thomas et al. [16] explored the spectroscopic properties of Sm3+ ions in lithium zinc borate glasses and further investigated the dielectric properties. Ahamed et al. [1] studied the lasing potentials of Sm3+ doped lithium fluoroborate glasses and confirmed the reddish-orange emission of Sm3+ ions from CIE 1931 colour chromaticity coordinates. Basavapoornima et al. [17] examined the concentration dependent spectroscopic properties of Sm3+ doped phosphate glasses by replacing the heavy metal oxide (PbO) content present in the host matrix with Sm3+ ion which gives detailed information about the role of PbO in Sm3+ doped phosphate glasses. The influence of modifier oxide in the luminescence behaviour of Sm3+ ions have been investigated and reported by Raghava rao et al. [18]. The UV to visible photon conversion of Sm3+ doped alkaline earth borate glasses were suggested for the 3

ACCEPTED MANUSCRIPT conversion of UV radiation of solar spectrum into visible photons and the same is suggested by Shen et al. [19] to enhance the efficiency of solar cell. The present work reports concentration dependent structural and optical properties of Sm

3+

doped Leadfluoro-borophosphate glasses characterized through XRD, FTIR, optical

absorption, emission and decay spectral measurements. The presence of fundamental

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vibrational units has been identified through FTIR spectral analysis and the presence of three different network forming units such as BO3, BO4 and PO4 have also been explored. The radiative properties and symmetry around the Sm3+ ions have been investigated using JuddOfelt (JO) theory and the radiative properties have been calculated and discussed. The characteristic emission colour and the colour temperature of the prepared glasses were

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examined through CIE 1931 chromaticity diagram. The decay profile of the 4G5/2 meta-stable state pertaining to the Sm3+ ions have been measured and reported. Luminescence quenching

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at higher concentration were observed and is discussed with the possible energy transfer between Sm3+−Sm3+ ions in the prepared glasses and the nature of interaction have also been analysed with Inokuti-Hirayama (IH) model and the observation were discussed and reported. 2. Experimental

Sm3+ doped Leadfluoro-borophosphate glasses have been prepared by following the

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melt quenching technique using high purity chemicals (Sigma-Aldrich) such as H3BO3, H6NO4P, Li2CO3, ZnF2, PbO and Sm2O3 as starting materials in the present study. The glass code and the composition of the prepared glasses are given below. BPLP0S

: 50B2O3+20 P2O5+10Li2O+10ZnF2+10PbO+0Sm2O3

BPLP0.1S

: 50B2O3+19.95 P2O5+10Li2O+10ZnF2+10PbO +0.05Sm2O3

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BPLP0.05S

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BPLP0.25S

: 50B2O3+19.90 P2O5+10Li2O+10ZnF2+10PbO +0.1Sm2O3

: 50B2O3+19.75 P2O5+10Li2O+10ZnF2+10PbO +0.25Sm2O3

BPLP0.5S

: 50B2O3+19.5 P2O5+10Li2O+10ZnF2+10PbO +0.5Sm2O3

BPLP1S

: 50B2O3+19 P2O5+10Li2O+10ZnF2+10PbO +1Sm2O3

BPLP2S

: 50B2O3+18 P2O5+10Li2O+10ZnF2+10PbO +2Sm2O3

Chemical composition of 15 gm batches were weighed, mixed thoroughly in an agate

mortar and the homogenous mixture was taken into a porcelain crucible and kept in the electrical furnace at 1200 ⁰C for 2 hours. The melt was then air quenched by pouring it on to a preheated brass plate keeping at 400 ⁰C and the glass was annealed for 8 hours to increase the mechanical strength and to reduce the thermal strain associated with the quenching process. The glasses were well polished on both sides to obtain transparency before further

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ACCEPTED MANUSCRIPT optical studies and all the measurements were carried out at room temperature (RT) environment only. The amorphous nature of the prepared glass was confirmed through X-ray diffraction studies using JEOL 8030C X-ray diffractometer employing CuKα radiation. The infrared spectra of the glass samples were recorded using Perkin-Elmer paragon 500 FTIR

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spectrometer and the optical absorption spectra were recorded using Jasco V-670 spectrophotometer in the wavelength range 300−1800 nm. The photoluminescence measurements were made using Perkin-Elmer LS55 spectrometer in the wavelength range 450–750 nm with a spectral resolution of ±1.0 nm. The lifetime measurements were made

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through a digital storage oscilloscope (Tektronix TDS1001B) interfaced to a personal computer that records and averages the signal. The density of the prepared glasses were determined by employing Archimedes principle with xylene as the reference liquid at room

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temperature and the refractive indices of the samples were determined using Abbe refractometer at sodium wavelength (589.3 nm) keeping methylene iodide containing sulfur solution as a contact liquid. The other physical properties such as reflection losses, polaron radius, field strength, molar refractivity, electronic polarizability and dielectric constant were also calculated using the relevant expressions reported in literature [11] and the results are

3. Theory

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presented in table 1.

3.1. Band gap and Urbach’s energy analysis

The band gap studies are important to analyze the solid state materials for various

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photonic applications and there are two types of optical transitions such as direct and indirect transitions are possible at the fundamental absorption edge of the crystalline and non-

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crystalline materials. In both the cases, electromagnetic waves interact with the electrons in the valence band and rose across the fundamental gap to the conduction band. In glasses, the conduction band is influenced by the glass forming anions and the cations play an indirect but significant role. The absorption coefficient α(ω) driven from the Mott and Davis theory have been used to establish the relationship between the band gap and absorption coefficient α(ω) and the same is expressed using the below given equation [9, 12] (αћω)r = B(ћω−Eg)

(1)

where, B is a constant known as Band tailing parameter, Eg is the optical band gap, ћω is the photon energy of the incident radiation and r is an index which can have values as 2, 2/3, 1/2 and 1/3 depending upon the nature of transition from the valance band to the conduction band 5

ACCEPTED MANUSCRIPT such as direct allowed, direct forbidden, indirect allowed and indirect forbidden transitions respectively [9]. The optical band gap values were obtained by extrapolating the linear region of the plot of (αћω)r versus E (i.e. ћω) to zero absorption and the intersection of E gives the optical band gap value. Urbach’s energy gives the exponential behavior of the absorption coefficient near the

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band edge (λe ) and is calculated using the below given Urbach’s empirical formula [9] α(ћω) = Cexp(ћω/∆E)

(2)

where, α is the absorption coefficient, C is the constant and ∆ is the Urbach’s energy. Urbach’s energy values were estimated from the graph plotted between ln(α) and hν and the =(ћω)/ ln (ω). 3.2. Oscillator strengths and Judd-Ofelt analysis

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∆E values are obtained by taking 1/slope of the linear portion of the curve i.e. ∆E

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The intensity of the absorption bands can be characterized through the oscillator strength values of the f‒f electronic transitions of the RE ions. The quantitative analysis of the oscillator strengths of the absorption bands were studied using Judd-Ofelt theory and the experimental oscillator strength (ƒexp) of the absorption bands were calculated from the relative areas under the absorption band of the individual transitions in the absorption spectra

f

exp=

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using the following expression [12],

2 . 303 mc 2 N πe 2

∫ ε (ν ) d ν

= 4 . 318 × 10 − 9 ∫ ε (ν ) d ν

(3)

where, m is the mass and e is the charge of an electron, c is the velocity of electromagnetic

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radiation in vacuum, N is the Avagadro’s number and ε(ν) is the molar absorptivity of the band at a wave number ν(cm−1). The theoretical oscillator strengths (ƒcal) of the induced

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electric dipole allowed transition J→J’ can be calculated following the Judd-Ofelt theory using the below given expression,

(

)

(

2  8π 2 mcν   n 2 + 2  λ ' ' f cal =   × ∑ λ = 2 , 4 , 6 Ω λ ΨJ U Ψ J .  3h(2 J + 1)   9n 

)

2

(4)

where, ν is the wave number (cm–1) of the transition from the ground state (ΨJ) to the excited state (Ψ’J’), h is the Plank’s constant, J and J’ is the total angular momentum of the ground state and excited state of the RE ion respectively, n is the refractive index, (n2+2)2/9n is the Lorentz local field correction accounts for the dipole-dipole transition, Ωλ is the JO intensity parameters and ║Uλ║ are the doubly reduced matrix elements of the unit tensor operator of 2

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ACCEPTED MANUSCRIPT the rank λ= 2, 4, 6 which are estimated from the intermediate coupling approximation for a transition from ΨJ to Ψ’J’. The hypersensitive transition of the absorption spectra possess higher reduced matrix element values ║Uλ║ hence the oscillator strength of the transitions possess larger values [16]. All the spectra of the rare earth ions arise from the 4f−4f intraconfiguration transitions within the shell which are forbidden by the parity selection rule of

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the electric dipole transitions. However, RE3+ ions incorporated in a glass host experience a non-centrosymmetric crystal field interaction. 3.3. Radiative properties

The radiative parameters such as transition probability (A), stimulated emission cross-

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section ( ) and branching ratios (βR) for the emission transitions of the Sm3+ ions have been calculated using the JO intensity parameters and refractive index of the prepared glasses [17].

using the following expression [12] A( Ψ J , Ψ ' J ' ) = Amd + Aed =

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The radiative transition probability (A) for the transition Ψ’J’→ΨJ have been determined  3  64π 4 n ( n 2 + 2) 2  × n S + S ed  md 3  9 3hλ ( 2 J + 1)  

(5)

where, Aed is the electric-dipole and Amd is the magnetic-dipole contributions, respectively. n(n2+2)2/9 is the local field correction for the electric dipole transition and n3 is the local field

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correction for magnetic dipole transition. The Sed and Smd are the electric and magnetic-dipole line strengths and can be expressed as

(

and

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S ed = e 2 ∑λ =2, 4,6 Ω λ ΨJ U λ Ψ ' J '

2

(

e2h 2 Ω λ ΨJ L + 2S Ψ ' J ' 16π 2 m 2 c 2

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S md =

)

(6)

)

2

(7)

The total radiative transition probability AT is the sum of the A(ΨJ,Ψ’J’) terms calculated over all terminal levels and is represented as, AT(ΨJ) = ΣA(ΨJ,Ψ’J’). The branching ratio (βR) can be obtained from the below given expression [12, 16]

β R (ΨJ , Ψ ' J ) =

A(Ψ J , Ψ ' J ' ) AT Ψ J

(8)

The experimental branching ratio values can be obtained from the relative areas under the individual emission bands to the total area under the emission spectra. The peak stimulated emission cross-section (σ ) can be calculated using the below given expression [12] 7

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σ

E P

λ 4p A = 8π cn 2 ∆ λ eff

(9)

where λp is the emission transition peak wavelength, n is the refractive index of the glass and ∆λeff is the effective line width of the transition which is calculated using the following

∆λeff =

1 I max

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equation [12]

∫ I (λ )dλ

(10)

where I is the fluorescence intensity and Imax is the intensity at band maximum.

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3.4. CIE chromaticity coordinates

The Commission Intenationale de I’Eclariage (CIE) is the standard reference to define the colours and is obtained by considering the sensitivity of the human eye to different

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colours. To characterize the colour of the visible emission from any electromagnetic source the CIE coordinates were calculated thus indicates the characteristic colour of the source when the human eye perceives the light source. The color of the luminescent source can be  (λ), ̅(λ) and they are described through the color matching function values ̅ (λ) ,  dimensionless quantities. The degree of stimulation required to match the color of the spectral  =  ̅ (λ)(λ)λ

(11)

 =   (λ)(λ)λ

(12)

! =  ̅ (λ)(λ)λ

(13)

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power density P(λ) is expressed as,

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where X, Y and Z are the tristimulus values which gives the power for each of the three primary colors to match with the color of P(λ) and from the tristimulus values the color

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chromaticity coordinates x and y can be determined from the following expressions [9], =

" "#$#% $

 = "#$#%

(14) (15)

The x, y coordinates are used to represent the color and locus of all the monochromatic color coordinates which produces the perimeter of the CIE 1931 chromaticity diagram. All the multi chromatic wavelengths are expected to lie within the area of the chromaticity diagram. The correlated color temperature (CCT) has been calculated using the color coordinates employing the McCamy’s approximate formula [9] CCT = −449n3+3525n2−6823n+5520.33

(16)

where n = (x − xe)/(y −ye) is the inverse slope line and xe = 0.332, ye = 0.186 is the epicentre. 8

ACCEPTED MANUSCRIPT 3.5. Decay analysis The intensity of the luminescence spectra for single exponential (lower concentration) can be expressed using the below given formula, & = &' + )*+(─-/)

(17)

and for non-exponential (higher concentration) is & = &' + )/ *+(─-/τ/ ) + )0 *+(─-/τ0 )

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(18)

where, A1 and A2 are constants, τ1 and τ2 are the luminescence lifetimes for the two channels responsible for the decay and the experimental lifetime values (τexp) were calculated using the below given relation, 4 4

6 6

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(3 56 #3 56 )

12 = (3 45 4#3 4 56 )

(19)

The non-radiative decay is due to the cross- relaxation between Sm3+−Sm3+ ions [12] 78 = τ

/

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and is calculated using the below given expression, 9:;

−τ

/

<=>

(20)

where, WNR= WCR, and WCR denotes the cross-relaxation rate and this factor contribute to the non-radiative decay (WNR).

The Inokuti-Hirayama (IH) model is used to analyse the nature of energy transfer

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process takes place between the Sm3+−Sm3+ ions [12] and to evaluate the energy transfer parameters. The IH model is valid when the energy transfer process between the donor and acceptor ion is appreciably faster than the energy diffusion between the donors. According to IH model, the emission intensity is expressed as [16],

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3/ S  t  t   I (t ) = I 0 exp− − Q    τ 0  τ 0  

(21)

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where, S = 6, 8 and 10 for dipole-dipole, dipole-quadrupole and quadrupole-quadrupole interaction between the RE3+ ions, t is the time after excitation, τ0 is the intrinsic decay time of the donors in the absence of acceptors, Q is the energy transfer parameter defined as [16], Q=

4π  3 Γ1 −  N 0 (C DA ) 3/S 3  S

(22)

Γ(x) is equal to 1.77 for dipole-dipole (S=6), 1.43 for dipole-quadrupole (S=8) and 1.3 for quadrupole-quadrupole (S=10) interactions respectively. N0 is the concentration of the acceptor ions in ions/cc which is almost equal to the concentration of the RE3+ ions and CDA donor-acceptor interaction parameter or also known as energy transfer rate.

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ACCEPTED MANUSCRIPT 4. Results and discussion 4.1. XRD analysis The X-ray diffraction (XRD) pattern of the prepared glasses has been recorded in the range 5˚≤θ≤80˚. The broad diffused scattering at lower angles observed in the XRD pattern confirms the amorphous nature and as a representative case XRD pattern of the BPLP0.5S

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glass is shown in Fig. 1.

4.2. FTIR spectra

Fig. 2 shows the FTIR spectra of the present BPLPxS glasses and the peak assignments for the various fundamental stretching units of the borate and phosphate networks are presented in table 2 along with their band positions. The Zn‒O stretching

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vibration was confirmed from the observed band position around 466 cm−1 [9] and the band centered at 559 cm−1 is due to the bending modes of PO4 and P─O─B groups. The vibration

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at 700 cm−1 was assigned to both B‒O‒B bending and symmetric stretching vibrations of P−O−B linkage and the symmetric stretching of the BO4 and PO4 units were confirmed from the band centered at 1042 cm‒1. The band observed around 1273 cm−1 is due to the vibration of P=O linkages present in the network [20] and the band at 1466 cm−1 is assigned to the stretching vibrations of B–O bonds of BO3– units involving the linkage oxygen connecting

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different groups [21]. The combined vibration of B−O asymmetric stretching of BO3 units and P=O linkage vibrations were observed around 1562 cm−1 and the vibrational band at 1652 cm−1 confirm the conversion of BO3 units into BO4 units in the glass network. The presence of OH, P‒OH and B‒OH groups were observed at around 1749 cm−1. The bands

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found in the region 2829−2990cm−1 is due to the formation of hydrogen bond between P−OH and O−Zn units [9]. The broad band around 3440 cm−1 is due to the presence of OH¯

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stretching vibrations in the prepared glasses. Sm2O3 content in the Leadfluoro-borophosphate glasses act as a network modifier and

the introduction of Sm2O3 into the prepared glasses modify the glass network because of the fact that the absorption band due to boron orthophosphate (P−O−B) unit get disappear at 560 cm−1 meanwhile the absorption intensity of both [BO3] stretching band at around ~1466 cm−1 and the [BO4] stretching band at around ~1057 cm−1 are found to increase. It shows that B3+ ion can exist in the form of both [BO4] tetrahedra and [BO3] trihedral coordinate in the prepared glasses [21]. Further, increasing the Sm2O3 content increases the intensity of both the bands around 560 cm−1 and 1652 cm−1 thus indicates the increasing P−O−B bond in the network due to the conversion of more number of BO3 units into BO4 units. The ratio 10

ACCEPTED MANUSCRIPT between the peaks at ~1466 cm−1 and ~1057 cm−1 decreases which confirms the decreasing number of BO3 units than BO4 units in the prepared glasses with increasing Sm2O3 content.

4.3. Optical absorption spectra and Nephelauxetic effect Fig. 3 shows the UV-Vis-NIR absorption spectra of the present BPLPxS glasses recorded in the wavelength region 350−1800 nm. Though the absorption spectral profile of

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the prepared glasses is found to be alike they exhibit slight differences in their intensities. Each spectrum exhibit twelve absorption bands due to the 4f−4f transition of the Sm3+ ions from the 6H5/2 ground state to the various excited energy levels such as 6P3/2, 6P5/2, 4M19/2, 4

I15/2, 4I13/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2 and 6F1/2 centered at 400, 414, 420, 439, 459,

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474, 939, 1074, 1225, 1372, 1476 and 1583 nm respectively [23]. Further it is observed from the Fig. that the transitions of the Sm3+ ions observed in the UV region are very weak due to the strong host lattice absorption. The transitions from the 6H5/2 ground state to the 6H and 6F

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transitions are spin allowed (∆S = 0) and the transitions appear in the NIR region is found to be more intense. The transitions which obey the selection rules |∆S|=0, |∆L|≤2 and |∆J|≤2 are highly influenced by the chemical environment around the RE ion site and are known as hypersensitive transitions which are highly sensitive to the host environment as well as the RE ion concentration due to the inhomogenity in the ligand field environment [12]. Among

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the twelve absorption transitions, 6H5/2 → 6P3/2, 6F3/2 and 6F1/2 transitions of the Sm3+ ion obey the selection rule and the intensity of the same were highly influenced by the host matrix. The hypersensitive nature of the absorption transitions was observed from the nephelauxetic effect which helps one to predict the nature of the bonding between RE3+ ion and the host

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matrix. The nephelauxetic ratio (β) is the ratio between the observed energy (in cm‒1) for a particular absorption transition of the RE3+ ion in the host to the corresponding absorption

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transition of the aqua ion [24]. The average nephelauxetic ratio (?̅ ) values are calculated and presented in table 3 and from the ?̅ values, blue shift in the energy positions of the absorption transition could be observed and is due to the nephelauxetic effect [9]. The nature of bonding between the Sm3+ ions with the ligand field can be studied from the bonding parameter (δ) values and is evaluated from the average values of the nephelauxetic ratios @?̅ A using the below given relation [11, 25]

δ=

) (/BC  C

× 100

(23)

Depending upon the ligand field environment, δ value can either be positive or negative with respect to covalent or ionic nature of the bond between RE ions and the ligand field environment and the calculated bonding parameter (δ) values of the title glasses are 11

ACCEPTED MANUSCRIPT presented in table 3. The negative bonding parameter values for all the prepared glasses indicate the ionic nature of the Sm−O ligand bond. If the interaction between oxygen ions and the host matrix is higher, it decreases the effect of oxygen influence on the RE3+ ions. According to the electronegativity theory, the RE3+ ions bonded with P−O− unit is more covalent than the B−O− unit [24]. In the present work, B−O−P bond formation dominates the

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glass network upto 0.5 wt% of Sm2O3 content which is observed from the FTIR spectra corresponding to the 559 cm−1 vibrational peak in the prepared glasses. Hence, NBO of the BO4 group construct a new B−O−P bonds in the glass network upto 0.5 wt% of Sm2O3 and the probability of formation of B−O−Sm bond decreases than the formation of P−O−Sm bond

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which decreases the ionic nature of the Sm−O bond upto 0.5 wt% of the Sm2O3 content in the prepared glasses. The intensity of the 559 cm−1 vibrational band didn’t get change and the

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intensity of the vibrational band centered at 1652 cm−1 is found to increase. It signifies that the number of BO3 units converted into BO4 units increases and the probability of formation of B−O−Sm bond with the NBO of BO4 unit increases. Therefore the ionic nature of the Sm−O bond increases beyond 0.5 wt% of Sm2O3 content.

4.4. Band gap and Urbach’s energy analysis

The Tauc’s plots of the prepared glasses are shown in Fig. 4 and the direct band gap

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values are found to be 3.27 eV, 3.28 eV, 3.26 eV, 3.26 eV, 3.25 eV, 3.24 eV and 3.23 eV corresponding to the BPLP0S, BPLP0.05S, BPLP0.1S, BPLP0.25S, BPLP0.5S, BPLP1S and BPLP2S glasses respectively. The indirect band gap values vary from 3.12 to 3.05 eV

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following the same trend as that of the direct band gap values and the band tailing parameter values are calculated and the results are presented in table 4. It is observed from the table that while introducing the Sm3+ ions into the host matrix the direct and indirect band gap values

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are found to increase upto 0.05 wt% of Sm2O3 content and after that it starts to decrease. This indicates the fact that the wavelength of the optical absorption edge of the prepared glasses initially (0.05 wt% of Sm2O3 content) shift toward the higher energy side due to the formation of bond between NBO and the Sm3+ ions. Further increment in the Sm2O3 content starts to shift the absorption edge towards the lower energy side of the electromagnetic spectrum due to the formation of more number of NBOs created in the host matrix by the structural rearrangement of BO3 units into BO4 units– because of the fact that NBOs binds excited electrons less tightly than the bridging oxygen [26]. The band tailing parameter values are found to decrease with the increase in Sm3+ ion content and is attributed to the decrease in degree of disorder and the defects present in the title glasses. 12

ACCEPTED MANUSCRIPT Urbach’s energy related to the optical transition between the tail end of the valance band and the conduction band which is extended into the band gap and is used to characterize the degree of disorderness in the amorphous materials [27]. The ∆E values are found to vary between 0.263 eV and 0.353 eV and the presence of minimum number of defects which assist the long range order in the prepared glasses were confirmed through the lower Urbach’s

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energy values and the changes in the ∆E value is due to the defects produced within the localized states [27]. It is observed from table 4 that the band gap and the Urbach’s energy values follow the opposite trend i.e. when the band gap values decreases the Urbach’s energy values are found to increase due to the Sm3+ ions content in the prepared glasses which may

rearrangement in the glass network.

4.5. Oscillator strengths and Judd-Ofelt analysis

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delocalize some of the localized states present in the energy levels through the structural

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The experimental oscillator strength values have been used to calculate the JO intensity parameters (Ωλ=2, 4, 6) following the least square fitting method and the oscillator strength values (×10−6) of the prepared glasses are presented in table 5 along with rms deviation (σ) values. It is observed from table 5 that the experimental and calculated oscillator strengths are having fine agreement for the hypersensitive and intense transitions in the NIR region and moderate agreement in the case of weak transitions. Reasonably lower

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rms deviation (< 0.6×10−6) found between the experimental and calculated oscillator strength values justifies the validity of the JO analysis. The JO intensity parameters signifies the symmetry around the RE ion site as well as the nature of the bond between RE ions with its

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surrounding ligands. Among the JO intensity parameters, Ω2 parameter is more sensitive to the local structure and asymmetry around the RE ions whereas the Ω4 and Ω6 parameters

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depend on the bulk properties such as rigidity and viscosity of the glass host. The JO parameters follows the trend as Ω4>Ω6>Ω2 uniformly for all the prepared glasses and the values are presented in table 6 along with the reported Sm3+ doped glasses [1,17,28−32]. The lower value of the Ω2 parameter indicates the lower asymmetry around the Sm3+ ions interms of bonding nature, bond length, bond angle and also the ionic bond between Sm–O ligand in the prepared glasses due to the higher mixing of opposite parity electronic configurations that are responsible for large spectral intensities. The bonding parameter (δ) and the Ω2 parameter values behave alike in the prepared glasses and are shown in Fig. 5. The higher values of Ω4 parameter indicate the high rigidity of the glass medium around the Sm3+ ions. The JO parameter values suggest the symmetry of the site occupied by the Sm3+ ions in the prepared 13

ACCEPTED MANUSCRIPT glasses and is found to be higher than the reported glasses [1,17,28−32]. The spectroscopic quality factor (Ω4/Ω6) is an important parameter used to describe the optical quality of the prepared glasses and is calculated from the Ω4/Ω6 ratio values of the title glasses and the values are comparable with the reported Sm3+ doped glasses [1,17,28−31].

4.6. Excitation and Emission spectra

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Fig. 6 shows the emission spectra of the Sm3+ doped Leadfluoro-borophasphate glasses and the corresponding excitation spectrum is shown in the inset of Fig. 6. The excitation spectrum of the BPLP0.5S glass was recorded in the wavelength region 200−500 nm by monitoring an emission wavelength at 598 nm. The excitation spectrum exhibit charge 6

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transfer band at around 263 nm and several excitation bands due to the transition from the H5/2 ground state to the various excited states such as 4D7/2, 4D3/2, 6P7/2, 6P3/2, 6P5/2, 4G9/2, 4I13/2

and 4I11/2 centered at 344, 361, 374, 402, 416, 438, 466 and 476 nm respectively. Among the

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excitation bands, 6H5/2→6P3/2 transition centered at 402 nm possess higher intensity and the same is used as an excitation source for the emission measurements. The emission spectra of the Sm3+ doped Leadfluoro-borophasphate glasses have been measured in the spectral range 400−750 nm and the same exhibit four emission bands centered at 562 nm, 598 nm, 645 nm and 707 nm corresponding to the 4G5/2→6H5/2, G5/2→6H7/2, 4G5/2→6H9/2 and 4G5/2→6H11/2 transitions respectively similar to the reported

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4

Sm3+ doped glasses [1,32]. The 4G5/2→6H9/2 and 4G5/2→6H11/2 bands correspond to electric dipole transitions (∆J ≤ 6 and ∆L = 2) hence they are hypersensitive in nature. Other two emission transitions, 4G5/2→6H5/2 is purely of magnetic dipole in nature (∆J = 0) and the G5/2→6H7/2 has both electric and magnetic dipole contribution (∆J = ±1). The two emission

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4

bands centered at 598 nm (4G5/2→6H7/2) and 645 nm (4G5/2→6H9/2) dominates in the emission

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spectra and possess almost 80% of the branching ratio and the results are presented in table 7. The luminescence intensity of the emission transitions are found to increase with the increase in Sm3+ ion content upto 0.5 wt% and further increase in Sm2O3 content causes luminescence quenching due to the interaction between Sm3+–Sm3+ ions through cross-relaxation process. The ratio between electric dipole allowed and the magnetic dipole allowed transition

is known as asymmetric intensity ratio or R/O ratio and is used as a tool to examine the coordination environment around the Sm3+ ion site. It is observed from table 7 that the luminescent intensity ratio of the 4G5/2→6H7/2 and 4G5/2→6H5/2 transitions (R/O values) changes with the change in RE ion concentration. Though the higher symmetry around the Sm3+ ion site were predicted from the JO parameters, the electric dipole transition which 14

ACCEPTED MANUSCRIPT dominates in the emission spectra lead to have higher R/O intensity ratio values for the prepared glasses. The higher values of R/O ratio indicates no centre of symmetry around the RE ion site in the present glasses which creates charge separation and further induces electric dipole transition in the prepared glasses. The R/O intensity ratio of the title glasses are found to be 2.89, 2.77, 2.65, 2.51, 2.64 and 2.76 corresponding to the BPLP0.05S, BPLP0.1S,

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BPLP0.25S, BPLP0.5S, BPLP1S and BPLP2S glasses respectively. It is interesting to observe from these results that, the ratio of the 4G5/2→6H7/2 and 4G5/2→6H5/2 transitions decreases with the Sm3+ ion concentration up to 0.5 wt% and after that increases.

4.7. Radiative properties

The calculated radiative properties of the prepared glasses are presented in table 7.

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The branching ratio (βR) and stimulated emission cross-section ( ) values are the important parameters for laser applications. The experimental and calculated βR values are found to be 6

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higher for the 4G5/2 →6H7/2 emission transition and the βR values follow the trend as 4G5/2 → H7/2>6H9/2> 6H5/2>6H11/2 uniformly for all the prepared glasses. It is observed from table 7

that, the experimental branching ratio values are having good agreement with the theoretically calculated values using Judd-Ofelt theory. The higher branching ratio values for the orange (598 nm) emission indicate its potential for laser applications [1,12]. The effective

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band width (∆λeff) of all the prepared glasses are found to be less than 10 nm and is much less than the reported literature [1,12,16,17,34,35] which in turn enhances the monochromatic property (line width) of the lasers. The stimulated emission cross-section ( ) indicates the rate of energy extraction by the external stimuli from the optical material and is directly

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proportional to the transition probability (A) and inversely proportional to the effective band width (∆λeff). Of all the observed emission bands, 4G5/2→ 6H7/2 transition exhibit higher

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stimulated emission cross-section values( ×10−22 ) and they are found to be 8.5, 10.7, 10.9, 14.0, 9.09 and 8.67 corresponding to the BPLP0.05S, BPLP0.1S, BPLP0.25S, BPLP0.5S, BPLP1S and BPLP2S glasses respectively and the peak stimulated emission cross section

( ) values follow the trend as 4G5/2 → 6H7/2>6H9/2>6H11/2>6H5/2 for the prepared glasses and the  values are found to be comparable to the reported literature [1,12,17,34,35]. Among the prepared glasses, BPLP0.5S glass possesses higher transition probability and lower effective band width which in turn leads to have higher stimulated emission cross-section value. The higher stimulated emission cross-section value is an attractive feature for low threshold, high gain laser applications which are used to obtain continuous wave (CW) laser action. Among the prepared glasses, BPLP0.5S exhibit higher stimulated emission cross 15

ACCEPTED MANUSCRIPT section and branching ratio values for the 4G5/2 → 6H7/2 transition and is more suitable for potential laser applications in the intense reddish-orange region.

4.8. CIE chromaticity coordinates The luminescent intensity of the emission spectral measurements of the source has been characterized using the CIE 1931 chromaticity diagram. The CIE x,y color chromaticity

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coordinates of the Sm3+ doped Leadfluoro-borophosphate glasses have been determined and presented in table 8 along with the x,y color chromaticity coordinates of the reported Sm3+ doped glasses. The chromaticity coordinates are found to be (0.60,0.39), (0.60,0.39), (0.59,0.39), (0.60,0.39), (0.60,0.39) and (0.60,0.39) corresponding to the prepared

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BPLP0.05S, BPLP0.1S, BPLP0.25S, BPLP0.5S, BPLP1S and BPLP2S glasses respectively and are shown pictorially in Fig.7. It is observed from Fig. 7 that, the chromaticity coordinates of all the title glasses possess same chromaticity coordinates near to the reddish-

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orange region of the CIE 1931 chromaticity diagram. The x,y color chromaticity coordinates of the dominant wavelength for the present glasses is found to be 598 nm in the reddishorange region (0.61,0.39) and the color purity of the reddish-orange emission is found to be 99% which confirms the fact that the prepared glasses can emit reddish-orange light. The CCT values of the prepared glasses are presented in table 7 along with the

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reported Sm3+ doped glasses [17]. It is observed from table 7 that, BPLPxS glasses emit reddish-orange light (2914 K) and is comparable to the characteristic colour of the radiation emitted by a black body approximately at a temperature of 2914 K. It can be an alternative choice for the generation of new luminescence materials pertaining to reddish-orange

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emission and the present glasses can act as a promising candidate for reddish-orange light emitting diode applications under UV excitation.

4.9. Decay analysis

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The lifetime values corresponding to the 4G5/2 excited level of the Sm3+ ions in the

prepared glasses have been determined using the decay profile of the 4G5/2→6H7/2 transition (598 nm) by monitoring an exciting at 402 nm and the same is shown in Fig. 8. The decay profile of the prepared glasses exhibit single exponential for lower concentration upto 0.1 wt% and after that it turn to non-exponential in nature. The non-exponential nature of the decay profile may due to the energy transfer between the donor (excited Sm3+ ions) and the acceptor (unexcited Sm3+ ions) ions. The experimental lifetime values for the 4G5/2 excited level are found to be 2.346, 2.123, 1.763, 1.492, 1.196 and 1.034 ms corresponding to the BPLP0.05S, BPLP0.1S,

16

ACCEPTED MANUSCRIPT BPLP0.25S, BPLP0.5S, BPLP1S and BPLP2S glasses respectively and the calculated lifetime (τR) values were obtained following the JO theory using the below given relation

τ (ΨJ) = [ΣAT(ΨJ)]−1

(24)

The experimental and calculated lifetime values of the title glasses for the 4G5/2 excited level have been evaluated and presented in table 9. The higher ionic nature of the

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Sm−O bond reduces the transition probability hence the calculated radiative lifetime value is much larger compared to the reported Sm3+ glasses [12,36,40,41−45]. In general difference between τexp and τcal values arises due to the non-radiative relaxation (WNR) occur in the excited state Sm3+ ions in terms of multi-phonon relaxation (WMPR) and energy transfer

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through interaction between Sm3+−Sm3+ ions (WCR). In Sm3+ ions, the energy separation between the meta-stable state to the next nearest lower energy state is around 7000 cm−1 [38]

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which is very much higher than the phonon energy of the borophosphate glasses hence the multi-phonon relaxation is approximately negligible.

The energy transfer process involved is shown in Fig 9 and the non-radiative rates are found to increase from 252 to 780 s−1 with the increase in Sm3+ ion concentration in the prepared glasses. Fig. 9 shows the partial energy level diagram of the Sm3+ ion along with the possible cross-relaxation channels involved in the luminescence quenching for the higher

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concentration of Sm3+ ions in the title glasses. The possible CR channels in the present BPLPxS glasses are [36, 12]

CR 1: (4G5/2: 6H5/2) → (6F5/2: 6F11/2) CR 2: (4G5/2: 6H5/2) → (6F7/2: 6F9/2)

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CR 3: (4G5/2: 6H5/2) → (6F9/2: 6F7/2) CR 4: (4G5/2: 6H5/2) → (6F11/2: 6F5/2)

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Energy transfer through CR takes place between the Sm3+ ions in the 4G5/2 meta stable

state to the nearby unexcited Sm3+ ions in the 6H5/2 ground state. The energy difference between 4G5/2 state to the intermediate levels of the Sm3+ ions such as 6F5/2, 6F7/2, 6F9/2 and 6

F11/2 are found to be around 1377 nm, 1167 nm, 1029 nm and 945 nm respectively which

occurs in resonance with the transition from the 6H5/2 ground state to the various excited states such as 6F11/2, 6F9/2, 6F7/2 and 6F5/2 at around 1381 nm, 1234 nm, 1081 nm and 947 nm respectively. After that these ions quickly decay non-radiatively from the intermediate states to the ground state [36]. The non-exponential nature of the decay profiles are well fitted to the I–H model with S=6 than S=8 and S=10 thus indicates that the dipole-dipole interaction dominates in the 17

ACCEPTED MANUSCRIPT prepared BPLPxS glasses compared to the dipole-quadrupole and quadrupole-quadrupole interactions which takes place between Sm3+−Sm3+ ions. The Q and CDA values are also obtained and compared with the reported literature [12,34,36,40,41,45] and the results are presented in table 9. The Q and CDA values are found to increase with the increase in Sm3+ ion concentration which in turn confirms the possible cross-relaxation between Sm3+–Sm3+

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ions consequently reducing the experimental lifetime of the 4G5/2 meta stable state of the Sm3+ ions in the present glasses and the same is graphically shown in Fig.10.

The internal luminescence quantum efficiency (η) is defined as the ratio between the numbers of photons emitted to the numbers of photons absorbed by the RE3+ ions. For RE3+

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doped glasses, it is equal to the ratio between the experimental lifetime (τexp) to the calculated lifetime (τcal) of the respective meta stable state and is given by η =(τexp/τcal)×100% [12]. The

η values for the BPLP0.05S, BPLP0.1S, BPLP0.25S, BPLP0.5S, BPLP1S and BPLP2S

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glasses are found to be 41, 47, 43, 37, 22 and 19 respectively and the results are presented in table 9 along with the reported Sm3+ doped glasses.

The laser parameters such as optical gain bandwidth and optical gain are important for the development of new optical devices and the optical gain bandwidth  ×∆λeƒƒ (×10−28 cm3) and optical gain  ×τR (×10−28 cm2s) values of the prepared glasses have been

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calculated and presented in table 9. It is observed from the tabulated results that among the prepared glasses, BPLP0.5S glass is found to be more suitable for developing visible lasers and fiber optic amplifiers since it exhibit higher magnitude of  ,  ×∆λeƒƒ,  ×τR,

5. Conclusion

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stimulated emission cross-section and branching ratio values. Structural and spectroscopic properties of Sm3+ ions doped title glasses have been

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studied and reported for laser gain medium and light emitting diode applications by varying the concentration of the RE ion. The amorphous nature was confirmed through the XRD pattern and the presence of various structural units such as BO3, BO4 and PO4 and the creation of non-bridging oxygen with increasing Sm3+ ions concentration were identified through FTIR analysis. The blue shift in the absorption transitions was identified from the nephelauxetic ratio and the negative δ values reveal the ionic nature of the Sm−O bond in the title glasses. The JO intensity parameters follows the trend as Ω4>Ω6>Ω2 uniformly for all the prepared glasses and the lower Ω2 values indicate the higher symmetry around the Sm3+ ion site. The luminescence quenching occurs beyond 0.5 wt% Sm3+ ion content in the prepared 18

ACCEPTED MANUSCRIPT glasses due to the Sm3+−Sm3+ ions interaction through cross-relaxation process. The higher R/O ratio thus indicates no centre of symmetry around the Sm3+ ion site which induces the electric dipole transition in the title glasses. The CIE colour chromaticity coordinates are found to lie in the reddish-orange light region and almost all the prepared glasses possess (x,y) values in the same point nearest to the wavelength 598 nm. The colour purity of the

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emission wavelength is 99 % and the CCT value 1627 K is comparable to the commercially available red light emitting source and the same is suggested for reddish-orange light emitting applications.

The decay profile of the 4G5/2 excited level is found to be single exponential upto 0.1

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wt% of Sm3+ ion content and after that it turn to non-exponential nature. The non-exponential behavior arises due to the efficient energy transfer between the Sm3+ ions through various cross-relaxation channels. The decay profile of the 4G5/2 excited level has been analyzed using

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the IH model fitted to S=6, thus indicates the dipole-dipole interaction. Among the prepared glasses, BPLP0.5S glass exhibit higher stimulated emission cross section(  ), branching ratio (βR), optical gain ( × ), and gain band width (  ×∆λeff) values corresponding to the 6

H7/2 emission band specifies its suitability for LED and visible laser applications.

Acknowledgment

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One of the authors Prof. K.Marimuthu would like to thank University Grants Commission, New Delhi for the sanction of financial support in the form of a major research Project No. F.No.41-916/2012 (SR). Mr. M.Vijayakumar is also thankful to the University

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project.

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Grants Commission, New Delhi for the financial support through Project Fellow in the above

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ACCEPTED MANUSCRIPT References 1. Sd. Z.A. Ahamed, C. M. Reddy, B. D. P. Raju, Specrochim. Acta Part A Mol. Biomol. Spectrosc., 103 (2013) 246–254 2. Y. Zhang, Z. Zhu, W. Zhang, Y. Qiao, J. Alloys Compd., 566 (2013) 164–167 3. A. Tarafder, A.R. Molla, S. Mukhopadhyay, B. Karmakar, Opt. Mater., 36(9) (2014)

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1463−1470 4. F. Nawaz, Md.R. Sahar, S.K. Ghoshal, A. Awang, I. Ahmed, Physica B 433 (2014) 89–95

5. V.B. Sreedhar, Ch. Basavapoornima, C.K. Jayasankar, J. Rare Earths, 32(10) (2014)

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918–926

6. B. Zhu, S. Zhang, G. Lin, S. Zhou, J. Qiu, J. Phys. Chem. C, 111 (2007) 17118–17121

Solids, 358 (2012) 782–787

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7. D. Umamaheswari, B.C. Jamalaiah, T. Sasikala, G. Kim, L.R. Moorthy, J. Non-Cryst.

8. W. Z. Tawfik, M.M. Mahdy, M.A.K. Elfayoumi, M.M. Elokr, J. Alloys Compd., 509 (2011) 10070–10074

9. M. Vijayakumar, K. Marimuthu,–J. Alloys Compd., 629 (2015) 230 241 10. Sk.N. Rasool, L.R. Moorthy, C.K.Jayasankar, Opt. Commun. 311 (2013) 156–162

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11. K. Selvaraju, K. Marimuthu, J. Alloys Compd., 553 (2013) 273–281 12. S. Arunkumar, K. Marimuthu, J. Alloys Compd., 565 (2013) 104 114 13. K. Swapna, Sk. Mahamuda, A.S. Rao, S. Shakya, T. Sasikala, D. Haranath, G.V. Prakash, Specrochim. Acta Part A Mol. Biomol. Spectrosc., 125 (2014) 53–60

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14. C. Venkateswarlu, M. Seshadri, Y.C. Ratnakaram, Opt. Mater., 33 (2011) 799 806 15. D. Ramachari, L.R. Moorthy, C.K. Jayasankar, Mater. Res. Bull. 48 (2013) 3607–

AC C

3613

16. S. Thomas, Sk.N. Rasool, M. Rathaiah, V. Venkatramu, C. Joseph, N.V. Unnikrishnan, J. Non-Cryst. Solids, 376 (2013) 106–116

17. Ch. Basavapoornima, C.K. Jayasankar, J. Lumin., 153 (2014) 233-241 18. P.R. Rao, G.M. Krishna, M.G. Brik, Y. Gandhi, N. Veeraiah, J. Lumin., 131 (2011) 212–217 19. L.F. Shen, B.J. Chen, E.Y.B. Pun, H. Lin, J. Lumin., 160 (2015) 138–144 20. S. Kumar, P. Vinatier, A. Levasseur, K.J. Rao, J. Solid State Chem., 177 (2004) 1723–1737 21. X. Feng, C. Qi, F. Lin, H. Hu, J. Am. Ceram. Soc., 82 (1999)3471–75 20

ACCEPTED MANUSCRIPT 22. M. Seshadri, M. Radha, D. Rajesh, L.C. Barbosa, C.M.B. Cordeiro, Y.C. Ratnakaram, Physica B 459 (2015) 79–87 23. W.T. Carnall, P.R. Fields, K. Rajnak, J. Chem. Phys., 49 (1968) 4424–4442. 24. X. Feng, C. Qi, F. Lin, H. Hu, J. Am. Ceram. Soc., 82(12) (1999) 3471–3475. 25. C.R. Kesavulu, C.K.Jayasankar, J. Lumin., 132 (2012) 2802–2809.

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26. Y. Chen,–Q. Nie, T. Xu, S. Dai, X. Wang, X. Shen, J. Non-Cryst. Solids, 354 (2008) 3468–3472.

27. B.H. Venkataraman, K.B.R. Varma, Opt. Mater., 28 (2006) 1423–1431.

28. V.D. Rodriguez, I.R. Martin, R. Alcala, R. Cases, J. Lumin. 54 (1992) 231−236.

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29. A.G. Souza Filho, P.T.C. Freire, I. Guedesi, F.E.A. Melo, M.C.C. Custodio, R. Lebullenger, A.C. Hernandes, J. Mater. Sci. Lett. 19 (2000) 135–137.

Solids 217 (1997) 215–223.

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30. P. Nachimuthu, R. Jagannathan, V. Nirmal Kumar, D. Narayana Rao, J. Non-Cryst.

31. M. Seshadri, K.V. Rao, J.L. Rao, Y.C. Ratnakaram, J. Alloys Compd., 476 (2009) 263−270.

32. A. Mohan Babua, B.C. Jamalaiaha, T. Sasikala, S.A. Saleem, L. Rama Moorthy, J. Alloys Compd., 509 (2011) 4743−4747.

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33. A. Agarwal, I. Pal, S. Sanghi, M.P. Aggarwal, Opt. Mater. 32 (2009) 339–344. 34. B.C. Jamalaiah, M.V.V. Kumar, K.R. Gopal, Opt. Mater. 33 (2011) 1643–1647. 35. P. Srivastava, S.B. Rai, D.K. Rai, Spectrochim. Acta, Part A 60 (2004) 637–642.

3534.

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36. R. Praveena, V. Venkatramu, P. Babu, C.K. Jayasankar, Physica B 403 (2008) 3527–

37. Y. Zhang, Z. Zhu, W. Zhang, Y. Qiao, J. Alloys Compd. 566 (2013) 164–167

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38. Y.C. Ratnakaram, A. Balakrishna, D.Rajesh, M. Seshadri, J. Mol. Struct. 1028 (2012) 141−147

39. S. Sailaja, C.N. Raju, C.A. Reddy, B.D.P. Raju, Y.D. Jho, B.S. Reddy, J. Mol. Struct.

1038 (2013) 29–34

40. K.K. Kumar, C.K. Jayasankar, J. Mol. Struct. 1074 (2014) 496–502 41. B.C. Jamalaiah, J. Suresh Kumar, A. Mohan Babu, T. Suhasini, L. Rama Moorthy, J. Lumin. 29 (2009) 363. 42. K. Swapna, Sk. Mahamuda, A. SrinivasaRao, T. Sasikala, L. RamaMoorthy, J. Lumin. 146 (2014) 288–294.

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ACCEPTED MANUSCRIPT 43. D. Umamaheswari, B.C. Jamalaiah, T. Sasikala, Il-Gon Kim, L. Rama Moorthy, J. Non-Cryst. Solids 358 (2012) 782–787. 44. O.Ravi, C.M. Reddy, L. Manoj, B.D.P. Raju, J. Mol. Struct. 1029 (2012) 53−59 45. Sk. Mahamuda, K. Swapna, M. Venkateswarlu, A. Srinivasa Rao, Suman Latha

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Shakya, G. Vijaya Prakash, J. Lumin. 154 (2014) 410–424.

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ACCEPTED MANUSCRIPT Table 1: Physical properties of the Sm3+ doped Leadfluoro-borophosphate glasses Physical properties

BPBL0.05S

BPBL0.1S

BPBL0.25S

BPBL0.5S

BPBL1S

BPBL2S

1

Average molecular weight (g/mol)

94.085

94.201

94.552

95.136

96.305

98.641

2

Density (ρ) (g/cm3)

3.530

3.420

3.352

3.300

3.095

3.246

3

Refractive index (ηd)

1.608

1.611

1.612

1.613

1.614

1.615

4

Molar volume (VM) (cm3/mol)

26.651

27.542

28.205

28.827

31.118

30.391

5

Rare earth ion concentration ( N×1020) (ions/cc)

0.226

0.365

0.848

1.830

3.390

7.594

6

Polaron radius ( rp) (Å)

14.252

12.141

9.173

7.097

5.778

4.417

7

Inter ionic distance ( ri ) (Å)

35.370

30.132

22.766

17.613

14.341

10.961

8

Field strength (F × 1013) (cm2)

2.398

3.304

9

Electronic polarizability (αe ×10−22)

36.547

22.686

10

Molar refractivity (Rm)

1.469

1.523

11

Dielectric constant (ε)

2.586

12

Reflection losses (R) (%)

5.434

9.671

14.586

24.970

9.797

4.542

2.455

1.097

M AN U

SC 5.788

1.555

1.582

1.689

1.613

2.595

2.599

2.602

2.604

2.608

5.476

5.490

5.504

5.517

5.531

TE D EP AC C

RI PT

Sl.No

ACCEPTED MANUSCRIPT Table 2: Peak table of FTIR spectra (in cm−1) of the Sm3+ doped Leadfluoro-borophosphate glasses Sl. No.

Band position (cm−1)

1

3440

2

2829–2990

3

1749

Presence of OH group, P‒OH and B‒OH vibrations.

4

1652

BO3 units changes into BO4 units

5

1562

Band assignments Fundamental stretching of OH group

RI PT

Hydrogen bond between P‒OH and O‒Zn units

Combined vibration of asymmetric stretching of B−O of BO3 units and

SC

P=O linkages

Stretching vibrations of the B–O bonds of (BO3)– units involving the

6

1466

7

1273

Vibration of P=O linkages

8

1042

Symmetric stretching of P–O–B links between BO4 and PO4 groups

9

700

B‒O‒B bending and symmetric stretching vibrations of P−O−B linkage

10

559

Bending modes of PO4 and P─O─B groups

11

466

Coupling of P−O and Zn−O bending modes for both PO4 and Zn−O groups

AC C

EP

TE D

M AN U

linkage oxygen connecting different groups

ACCEPTED MANUSCRIPT Table 3: Observed band positions (cm−1) and bonding parameters (
̅ and δ) of the Sm3+ doped Leadfluoro-borophosphate glasses

Sl. No

Transition from 6 H5/2→ 6 P3/2

Aqua ion [23] 24999

BPLP0.1S

BPLP0.25S

BPLP0.5S

BPLP1S

BPLP2S

24992

24996

24999

24941

24993

24939

P5/2

-

24093

24123

24150

24150

24156

24101

M19/2

23858

23845

23826

23815

23807

23810

23902

4

4

I15/2

22769

22783

22784

22781

22851

22953

22706

5

4

I13/2

21767

21778

21775

21737

21740

21735

21650

6

4

I11/2

-

21061

21099

7

6

F11/2

10671

10604

10649

8

6

F9/2

9308

9307

9312

9

6

F7/2

8174

8161

10

6

F5/2

7288

11

6

F3/2

12

6

21088

21096

21091

21096

10638

10638

10642

10517

9302

9314

9308

9136

8161

8165

8175

8167

7977

7291

7288

7291

7308

7293

7131

6783

6778

6777

6779

6788

6784

6641

F1/2

6312

6319

6316

6317

6318

6337

6397




1.0081

1.0071

1.0069

1.0065

1.0086

1.0087

-

δ

−0.7993

−0.7042

−0.6837

−0.6489

−0.8519

−0.8623

-

EP

TE D

4

AC C

3

SC

6

2

M AN U

1

RI PT

BPLP0.05S

ACCEPTED MANUSCRIPT Table 4: Fundamental absorption edge (λedge), optical band gap (Eopt), band tailing parameter (B) for the direct (n=2) and indirect (n=1/2) allowed transitions and Urbach’s (∆E) energy of the Sm3+ doped Leadfluoro-borophosphate glasses n=2

Sample code

λedge

Eopt (eV)

BPLP0S

362

BPLP0.05S

n=1/2

∆E (eV)

(cm–2 eV)

Eopt (eV)

B (cm–1/2 eV–1/2)

3.27

0.902

3.11

2234

359

3.28

0.906

3.12

2184

0.263

BPLP0.1S

363

3.26

0.898

3.10

2168

0.271

BPLP0.25S

364

3.26

0.868

3.10

2086

0.306

BPLP0.5S

366

3.25

0.823

3.09

BPLP1S

367

3.24

0.884

3.07

BPLP2S

367

3.23

0.894

TE D EP AC C

3.05

SC

RI PT

0.283

2036

0.314

2257

0.337

M AN U

B

2188

0.353

ACCEPTED MANUSCRIPT Table 5: Experimental and calculated oscillator strengths (×10−6), number of transitions (N) and rms deviation (σ) of the Sm3+ doped Leadfluoro-borophosphate glasses Sl. No

Transition from 6 H5/2→

BPLP0.05S

BPLP0.1S

BPLP0.25S

BPLP0.5S

BPLP1S

BPLP2S

ƒexp

ƒcal

ƒexp

ƒcal

ƒexp

ƒcal

ƒexp

ƒcal

ƒexp

ƒcal

ƒexp

ƒcal

6

P3/2

1.071

1.783

2.603

3.218

2.621

2.909

3.443

3.445

2.741

2.497

2.713

2.534

2

6

P5/2

0.681

0.268

0.260

0.000

0.071

0.000

0.370

0.000

0.049

0.000

0.048

0.000

M19/2

0.656

0.000

0. 329

0.406

0.069

0.361

0.035

0.432

0.019

0.314

0.019

0.318

4

4

I15/2

0.938

0.003

0.975

0.139

0.412

0.157

-

-

0.018

0.113

0.055

0.118

5

4

I13/2

0.136

0.296

0.068

0.369

0.058

0.425

0.059

0.448

0.032

0.307

0.070

0.320

6

4

I11/2

0.128

0.123

1.287

0.607

0.164

0.706

0.237

0.732

0.196

0.498

0.169

0.521

7

6

F11/2

0.479

0.300

0.568

0.323

0.239

0.385

0.311

0.311

0.237

0.271

0.245

0.284

8

6

F9/2

2.419

1.806

1.664

1.973

2.272

2.315

2.296

2.419

1.562

1.649

1.676

1.726

9

6

F7/2

1.965

2.402

3.060

2.886

3.258

3.181

3.543

3.417

2.447

2.364

2.515

2.456

10

6

F5/2

1.054

0.917

1.368

1.614

1.280

1.383

1.472

1.645

1.037

1.196

1.068

1.210

11

6

F3/2

0.765

0.554

1.634

1.068

0.992

0.740

1.115

0.851

0.796

0.614

0.805

0.618

12

6

F1/2

0.057

0.219

0 .144

0.507

0.036

0.195

0.031

0.189

0.027

0.130

0.018

0.127

N

12

14

σ

± 0.585

AC C

SC

12

12

11

12

12

±0.447

±0.257

±0.255

±0.185

±0.180

EP

13

M AN U

4

TE D

3

RI PT

1

ACCEPTED MANUSCRIPT Table 6: Judd-Ofelt (×10−20 cm2) parameters and Spectroscopic quality factor (Ω4/Ω6) of the Sm3+ doped Leadfluoro-borophosphate glasses with the reported Sm3+ doped glasses Ω2

Ω4

Ω6

Ω4/Ω6

Trend

References

BPLP0.05S

0.522

2.067

1.613

1.28

Ω4> Ω6>Ω2

[Present]

BPLP0.1S

0.544

2.771

2.194

1.26

Ω4> Ω6>Ω2

[Present]

BPLP0.25S

0.635

2.619

2.461

1.06

Ω4> Ω6>Ω2

[Present]

BPLP0.5S

1.525

2.939

2.712

1.08

Ω4> Ω6> Ω2

[Present]

BPLP1S

0.360

2.137

1.840

1.16

Ω4> Ω6>Ω2

[Present]

BPLP2S

0.348

2.163

1.928

1.12

Ω4> Ω6> Ω2

[Present]

LCZSFB

2.44

8.54

6.40

PKAPbNSm10

2.61

5.87

3.22

Fluorozincate

0.68

3.77

2.15

PbO− PbF2−B2O3

1.28

2.78

PbO− PbF2

1.16

Li-Phosphate Na-Phosphate

AC C

SC

[1]

1.82

Ω4> Ω6> Ω2

[17]

1.75

Ω4> Ω6> Ω2

[28]

1.97

1.41

Ω4> Ω6> Ω2

[29]

2.60

1.40

1.86

Ω4> Ω6> Ω2

[30]

0.83

4.10

3.34

1.22

Ω4> Ω6> Ω2

[31]

0.47

2.00

1.70

1.17

Ω4> Ω6> Ω2

[31]

M AN U

Ω4> Ω6> Ω2

0.43

1.28

1.03

1.24

Ω4> Ω6> Ω2

[31]

1.30

3.08

1.54

2.00

Ω4> Ω6> Ω2

[32]

EP

LTTSm10

1.35

TE D

Li-Na-Phosphate

RI PT

Sample code

ACCEPTED MANUSCRIPT Table 7: Emission band position (λP) (nm), effective band width (∆λeff) (nm), radiative transition probability (A) (s−1), peak stimulated emission cross-section ( ×10−22) (cm2), Red to Orange (R/O) intensity ratio, calculated (βcal) and experimental (βexp) branching ratios of the Sm3+ doped Leadfluoro-borophosphate glasses

4

4

BPLP0.1S

BPLP0.25S

BPLP0.5S

BPLP1S

BPLP2S

λP

562

562

562

562

562

562

∆λeff

6.6

6.9

6.9

7.2

6.7

6.6

A

19.04

21.47

20.39

21.13

19.92

19.86



1.46

1.57

1.50

1.49

1.54

1.51

βcal

0.109

0.087

0.092

0.087

0.108

0.107

βexp

0.112

0.119

0.126

0.117

0.117

0.115

λP

597

597

597

597

597

597

∆λeff

6.2

6.4

6.4

5.4

6.5

6.4

A

80.88

104.8

107.26

117.9

89.42

87.12



8.5

10.7

10.9

14

9.09

8.67

βcal

0.465

0.426

0.485

0.486

0.474

0.478

βexp

0.492

0.488

0.442

0.501

0.512

0.495

λP

644

644

644

644

644

644

∆λeff

5.3

5.1

5. 5

5.5

5.0

4.1

A

36.65

46.63

51.99

66.89

37.49

37.06

6.11

7.42

8.28

11.6

7.93

6.52

0.211

0.272

0.211

0.215

0.202

0.200

0.325

0.317

0.349

0.293

0.310

0.317

G5/2→6H7/2

G5/2 →6H9/2

 βcal

EP

βexp λP

707

707

707

707

707

707

∆λeff

7.3

9.0

8.8

10.3

7.4

8.8

A

16.11

24.24

23.36

26.87

19.20

19.65



2.84

3.43

3.38

3.31

3.27

2.86

βcal

0.093

0.099

0.106

0.111

0.105

0.105

βexp

0.071

0.076

0.083

0.089

0.061

0.073

2.89

2.77

2.65

2.51

2.64

2.76

AC C

4

G5/2→6H11/2

R/O ratio

SC

G5/2→6H5/2

RI PT

BPLP0.05S

M AN U

4

Parameter

TE D

Transition

ACCEPTED MANUSCRIPT Table 8: CIE 1931 chromaticity coordinates (x,y) and correlated color temperature (CCT, K) of the Sm3+ doped Leadfluoro-borophosphate glasses with the reported Sm3+ doped glasses Chromaticity coordinates

References

0.39

1620.7

[Present]

0.60

0.39

1620.7

[Present]

BPLP0.25S

0.59

0.39

1620.6

[Present]

BPLP0.5S

0.60

0.39

1621.0

[Present]

BPLP1S

0.60

0.39

1621.2

[Present]

BPLP2S

0.60

0.39

1621.1

[Present]

Sm3+: LBZLFB

0.62

0.36

-

[1]

KNSZLSm10

0.59

0.41

PKAPBNSm10

0.59

0.40

PPNSm

0.59

TZKC

0.59

PbFPSm

0.48

Calcium borosilicate

0.60

BPLP0.05S

0.60

BPLP0.1S

[15]

1626

[17]

0.4

2152

[17]

0.40

2152

[17]

0.34

1919

[17]

0.40

-

[37]

TE D EP AC C

-

M AN U

Y

RI PT

CCT

x

SC

Sample code

ACCEPTED MANUSCRIPT Table 9: The calculated (τcal, ms) and experimental (τexp, ms) lifetime, energy transfer parameter (Q), donor-acceptor interaction parameter (CDA,×10−43 cm6/s), optical gain bandwidth (  ×∆λeƒƒ×10−28 cm3), optical gain (  ×τR×10−24 cm2 s), figure of merit ( ×τexp×10−24 cm2 s), internal quantum efficiency (η %) and the non-radiative transition rate (WNR, s−1) of the Sm3+ doped Leadfluoro-borophosphate glasses with the reported Sm3+ doped glasses

τexp

Q

CDA

 ×∆λeƒƒ

 ×τR

 ×τexp

η

WNR

References

BPLP0.05S

5.751

2.346

-

-

5.29

4.88

1.99

41

252

[present]

BPLP0.1S

4.521

2.123

-

-

6.83

4.34

2.27

47

250

[present]

BPLP0.25S

4.125

1.763

0.719

1.194

6.98

4.94

1.93

43

325

[present]

BPLP0.5S

4.063

1.492

1.233

3.615

7.66

5.77

2.09

37

424

[present]

BPLP1S

5.344

1.196

1.511

8.261

5.66

4.72

1.04

22

652

[present]

BPLP2S

5.444

1.034

1.944

13.114

5.78

4.86

9.41

19

780

[present]

1SmPbFB

2.880

0.864

2.173

3.73

-

-

-

30

819

[12]

-

1.75

0.518

5.50

-

-

-

41

338

[34]

2.820

1.896

0.05

2.200

-

-

-

58

260

[36]

-

0.640

-

-

-

-

-

58

645

[39]

1.66

1.52

1.41

2.59

-

-

-

-

-

[40]

-

0.860

0.43

13.08

-

-

-

18

955

[41]

Glass D

2.405

1.977

-

-

2.40

12.1

26.2

82

90

[42]

SFB

3.04

1.49

-

-

10.40

9.94

10.14

49

342

[43]

TMZNB

1.90

0.45

-

-

-

-

-

26

1634

[44]

TCZNB

2.81

0.52

-

-

-

-

-

27

1411

[44]

2.970

2.467

0.240

0.666

4.99

29.7

6.56

83

69

[45]

Sm3+:CdBiB PKACaLFSm10

AC C

EP

LBTAF:10

OFBSm01

SC

M AN U

PPNSm10

TE D

PKFBASm:2.0

RI PT

τcal

Glass code

RI PT

ACCEPTED MANUSCRIPT

20

30

EP

10

TE D

M AN U

SC

Counts

BPLP0.5S

40

2θ (degree)

50

60

AC C

Fig.1. XRD pattern of the BPLP0.5S glass

70

80

−1

RI PT

1043 cm

−1

457 cm

−1

700 cm −1 560 cm

SC 3000

2500

−1

M AN U 3500

TE D

4000

1660 cm −1 1569 cm −1 1466 cm −1 1273 cm

−1

1750 cm

Transmitance (a.u)

3440 cm

−1

−1

2920 cm −1 2856 cm

ACCEPTED MANUSCRIPT

BPLP2S BPLP1S BPLP0.5S BPLP0.25S BPLP0.1S BPLP0.05S BPLP0S 2000

−1

1500

1000

EP

Wave number (cm )

AC C

Fig.2. FT-Infrared spectra of the Sm3+ doped Leadfluoro-borophosphate glasses

500

ACCEPTED MANUSCRIPT

6

P3/2

6

Absorption intensity (a.u)

F7/2

F9/2

4

M19/2

4

4

I13/2 4 I11/2

I15/2

6

6

F5/2

6

SC

P5/2

F3/2 6

F1/2

M AN U

F11/2

400

TE D

350

6 6

450

1000

BPLP2S BPLP1S BPLP0.5S BPLP0.25S BPLP0.1S BPLP0.05S BPLP0S

RI PT

H5/2

6

1200

1400

1600

EP

Wavelength (nm)

AC C

Fig.3. Absorption spectra of the Sm3+ doped Leadfluoro-borophosphate glasses

1800

ACCEPTED MANUSCRIPT

RI PT

(cm 2.5

SC 3.0

M AN U

(αhν)

1/2

BPLP1S BPLP2S

2

2

(αhν) (cm eV)

-1/2

-1/2

eV )

BPLP0S BPLP0S BPLP0.05S BPLP0.05S BPLP0.1S BPLP0.1S BPLP0.25S BPLP0.25S BPLP0.5S BPLP1S BPLP0.5S BPLP2S

3.5

2.5

TE D

Energy (eV)

3.0

EP

Energy (eV)

AC C

Fig.4. Tauc’s plot for the direct band gap of the Sm3+ doped Leadfluoroborophosphate glasses [Inset shows the indirect band gap plot for all the present BPLPxS glasses]

3.5

ACCEPTED MANUSCRIPT

-0.60

1.6

Bonding parameter Ω2 parameter

RI PT

1.4

0.8

M AN U

-0.75

-0.80

-0.90 0.0

TE D

-0.85

0.5

1.0

0.6

0.4

0.2 1.5

2.0

EP

Sm2O3 content (wt%)

Fig.5. Comparison between the Bonding parameter and Ω2 parameter of the Sm3+ doped Leadfluoro-borophosphate glasses

2

1.0

Ω parameter

1.2

SC

-0.70

AC C

Bonding parameter

-0.65

ACCEPTED MANUSCRIPT

λemi= 598 nm

λexe= 402 nm

CT 6

RI PT

BPLP0.5S

H9/2

6 P7/2

4 4 6 P5/2 I13/2+ I11/2

4 D3/2

250

300

350

400

450

6

500

H5/2

M AN U

Wavelength (nm)

450

BPLP0.5S

4 G9/2

4 D7/2 200

G5/2

H7/2

SC

E xcitation intensity (a.u)

500

550

600

650

BPLP0.25S BPLP1S BPLP0.1S BPLP2S BPLP0.05S

6

H11/2

700

TE D

Wavelength (nm)

EP

Fig.6. Luminescence spectra of the Sm3+ doped Leadfluoro-borophosphate glasses [Inset shows the excitation spectrum of the BPLP0.5S glass]

AC C

Luminescene intensity (a.u)

6 H5/2

4

6

6 P3/2

750

RI PT

Green

SC

+

(xd,yd)

M AN U

(x,y)

White

(xe,ye)

+

Red

+

TE D

Blue

EP

x - chromaticity coordinate

Fig.7. CIE 1931 chromaticity diagram of the Sm3+ doped Leadfluoroborophosphate glasses

AC C

y - chromaticity coordinate

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

(a) BPBL0.05S (b) BPBL0.1S (c) BPBL0.25S (d) BPBL0.5S (e) BPBL1S (f) BPBL2S

λexe= 402 nm

RI PT

Log normalized intensity (a.u)

λemi= 598 nm

a

SC

b d e

f

0

1

2

TE D

S=6 S=8 S=10

3

Exponential and non-exponential fit

M AN U

c

IH fit

4

5

6

7

8

9

EP

Time (ms)

AC C

Fig.8. Decay profile corresponding to the 4G5/2 energy level of the Sm3+ doped Leadfluoro-borophosphate glasses monitoring an emission at 598 nm

10

ACCEPTED MANUSCRIPT 3+

3+

28

Non-radiative phonon relaxation 4

20

6 F 6 11/2 F 6 9/2 F 6 7/2 F 5/2

CR1 CR2 CR3 CR4

M AN U

12

402 nm

16

562 nm 598 nm 644 nm 707 nm

G 5/2

8

0

Excitation

TE D

4

Emission

6 H 6 11/2 H 6 9/2 H 6 7/2 H 5/2

4 G 5/2

6 F 6 11/2 F 6 9/2 F 6 7/2 F 5/2 6 H 6 11/2 H 6 9/2 H 6 7/2 H 5/2

Cross relaxation

EP

Fig.9. Partial energy level diagram of the Sm3+ ions showing excitation, possible emission transitions, non-radiative decays and cross-relaxation channels in the Sm3+ doped Leadfluoro-borophosphate glasses

AC C

3 -1 Energy (×10 cm )

24

SC

4 D 4 7/2 D 6 3/2 P 6 7/2 P 6 3/2 P 4 5/2 G 4 9/2 I 4 13/2 I 11/2

RI PT

Sm ion

Sm ion

ACCEPTED MANUSCRIPT

2.4

SC

1.8

1.4

1.0 0.5

TE D

1.2

1.0

1.6 1.4

M AN U

1.6

1.8

1.2 1.0 0.8 0.6

1.5

2.0

EP

3+ Sm ions concentration (wt%)

Fig.10. Comparison between the experimental lifetime (τexp) and energy transfer parameter (Q) of the Sm3+ doped Leadfluoro-borophosphate glasses

Energy transfer parameter (Q)

RI PT

2.0

AC C

Lifetime (τexp, ms)

2.2

2.0

exp lifetime Q

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High lights
Blue shift in nephelauxetic effect reveals the ionicity of the Sm−O bond

RI PT


JO parameters follows the trend as Ω4>Ω6>Ω2 uniformly for all the BPBxS glasses
Higher R/O ratio indicates no centre of symmetry around the Sm3+ ion site


IH fitted to S=6 indicates dipole-dipole interaction dominates in the Sm3+−Sm3+ ions

AC C

EP

TE D

M AN U

SC


The colour purity of the emission wavelength is found to be 99 %