Multifunctional Character of Revived double perovskite for Device Applications

Journal Pre-proof Multifunctional Character of Revived double perovskite for Device Applications

B.N. Parida, D.K. Pattanayak, Bhagyashree Mohanty, R.K. Parida, S.K. Mohanty PII:

S0254-0584(20)30072-9

DOI:

https://doi.org/10.1016/j.matchemphys.2020.122690

Reference:

MAC 122690

To appear in:

Materials Chemistry and Physics

Received Date:

28 November 2019

Accepted Date:

19 January 2020

Please cite this article as: B.N. Parida, D.K. Pattanayak, Bhagyashree Mohanty, R.K. Parida, S.K. Mohanty, Multifunctional Character of Revived double perovskite for Device Applications, Materials Chemistry and Physics (2020), https://doi.org/10.1016/j.matchemphys.2020.122690

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Journal Pre-proof Multifunctional Character of Revived double perovskite for Device Applications B N Parida3, D K Pattanayak2, Bhagyashree Mohanty1, *1R K Parida and 4S K Mohanty 1Department of Physics, ITER, Siksha ‘O’ Anusandhan (Deemed to be) University, Bhubaneswar, Odisha, India 2Department of Physics, GIET University, Gunupur, Raygada. 3Department of Physics, Central Institute of Technology, Kokrajhar, (Deemed to be University, MHRD, Govt. of India) BTAD, Assam-783370, India 4Department of Physics, VSSUT, Burla, Sambalpur. The materials having multifunctional behavior are in the form of single crystal or poly crystalline. The present reports belong to polycrystalline samples of lead reducing double perovskite vanadates of Pb2-xSrxBiVO6 (0.5 ≤ x ≤ 1.5) oxide ceramics. To synthesize the present samples cost effective solid solution casting technique has been adopted. Their formation, density, phase identification as well as purity were verified through X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Fourier transmission Infra-red (FTIR) and RAMAN spectroscopy. The optical properties of the materials have been investigated by utilizing room temperature UV-Vis and photo luminescence (PL) spectroscopic analysis. It is observed the band gap of the materials were found to be in the range of 2.68–2.23eV from UV-Vis study which suggest materials can be useful for photo catalytic devices whereas PL emission spectra confirms they are may be useful as blue white LED devices. Presence of ferroelectricity in the materials was confirmed from dielectric as well as polarization study which allows their utility for multi-layer capacitor and memory devices. Transport and leakage characteristics of the materials were studied from loss tangent, impedance spectroscopy as well as modulus spectroscopy recorded at different conditions of frequency and temperature which may be useful for microelectronics. Keywords: Perovskite; X-ray diffraction; polarization; Impedance. *Corresponding author: E-mail: [email protected] , +919438134417

Journal Pre-proof 1.

Introduction

The smart materials having multifunctional behavior are usually in the form of single crystal or in polycrystalline. The structure of above form of materials are in the form of perovskite and their derivatives such as, double perovskite, tungsten bronze or pyrochlore types. The first ABO3 type mineral is CaTiO3 usually known as perovskite which is named after Russian mineralogist Leo Perovski. In this context a number of ABO3 type materials having multifunctional behavior have been reported by different material scientist. The discovery of ferroelectricity in BaTiO3 by Goodman attracted much to the mineralogist to accelerate the study in this direction. Although lots of lead free and lead based perovskites are reported by different material scientist. Among the reports lead based minerals are dominated because of its better device applications. Although lead free materials are under the replacement lead based minerals still today complete replacement is quite difficult. The elemental modification in compounds with perovskite structure and its derivatives becomes more ideal for exploration for new multi-functionalized materials. The unique properties of these materials are piezoelectricity, pyroelectricity, ferroelectricity, colossal magneto-resistance, superconductivity, spin polarized semi-metallic electrical conductivity [1-6]; ionic conductivity [7], magnetic orderings ranging from anti-ferromagnetic to ferri- and ferromagnetic [8], catalytic properties [9] and multiferroicity [10]. As a result, perovskite and double perovskite materials are of generous mechanical enthusiasm, with a wide scope of potential applications, for example, components for solar cells [11], electrode and electrolyte materials for fuel cells [12], dielectrics or piezoelectrics in electronic devices and sensors [13], magnetic memory devices [6]. So far literature reports reveals. Lead based multifunctional materials are found to be potential candidates for possible device fabrications [14–24] like thermally stabilized ceramic capacitors, radio communication filters, microwave devices, piezoelectric transducers, MEMS, IC devices, memory

Journal Pre-proof devices like FRAM and pyroelectric detector devices. In addition to the above bismuth and vanadium doped multifunctional materials are other potential candidates for device like, oxygen based sensors, solid oxide fuel cell, oxygen separator etc. [25, 26]. This is the main thought for selecting the lead based vanadate series of ceramics. In view of the above substantial applications of perovskite based ceramics, we have tried to explore lead reducing vanadium based double perovskite with general formula Pb2-xSrxBiVO6 (x=0.5, 1 and 1.5) for possible device fabrication. As discussed Bismuth doped Vanadates are exploited for fuel cell as well as sensor purpose authors are paying their interest to synthesize the above ceramics. In addition to these, Pb-O, Sr-O, Bi-O and V-O based dipoles may have very good ferroelectric and structural stability for various memory, sensor and detector devices. Our previous report, impedance spectroscopy of Pb2BiVO6 [27], Dielectric and Ferroelectric investigations of Barium doped double perovskite Pb2BiVO6 for Electronic and Optical devices [28],Ferroelectric and Optical Modulations of Double Perovskite Ba2BiVO6[29], Structural and optical properties of a revived Pb0.5Ba1.5BiVO6 perovskite oxide [30] and Optical and transport properties of new double perovskite oxide [31] given us further boost to investigate in lead reducing Sr modified vanadium based double perovskites. In the present investigation, polycrystalline lead lessening double perovskites are synthesized by cost effective solid solution casting techniques and studied their ferroelectric as well as optical behavior. 2. EXPERIMENTAL 2.1.

Synthesis:

The solid state solution casting technique was used to synthesize the series of lead reducing Sr doped polycrystalline samples Pb2-xSrxBiVO6(x=0.5, 1 and 1.5) at moderate temperature. The raw materials used for above compounds are PbO, SrCO3, Bi2O3 and V2O5. All these chemicals are from M/s LOBA Chemie pvt. Ltd. India and their purity more than 99%.On the basis of proper

Journal Pre-proof stoichiometry, the individual powders are dry grounded utilizing an agate-mortar and pestle for 1.5 hrs and 1.5 hrs through wet methanol. The residue powders are (kept within alumina crucible with lid) calcined at an optimized temperature of 750oC utilizing Muffle furnace. The temperature is optimized by repeated fired techniques. 2.2

Structure and microstructure characterization:

The alluring formation of compounds, quality and the auxiliary arrangement of the atoms in the unit cells were confirmed by utilizing the room temperature X-ray diffraction (XRD) data. For this purpose powder diffractometer (RIGAKU Japan ULTIMA IV with CuKα radiation 1.5405 Å) was used. The rate of scanning to achieve room temperature XRD data is 2o/ minute within Bragg’s angle (2θ) (20o≤2θ≤ 80o). The calcined samplesare made into cylindrical pellets of diameter 10mm with thickness 0.5 – 2mm by using a hydraulic press with the application of pressure of about 4x106N/m2. To decrease the brittleness of the pellets polyvinyl alcohol (PVA) is added to the powered samples which evaporates during sintering at high temperature. The sintering temperature was optimized at 780oC after repeated firing. The optimized temperature was maintained for 4hrs in air atmosphere. The room temperature surface morphology of the sintered pellets were investigated by using Scanning Electron Microscope (SEM) (Model: JOEL JSM 5800). 2.3

Optical measurements:

In addition to XRD, room temperature RAMAN and FTIR data have been carried out to strengthen the phase For identifying the molecular vibration of the samples, Raman spectra are recorded at room temperature. NIR Raman Spectrometer was used for the study of Raman Spectra.MicroRaman Spectrometer was used takingAr+ laser as the source for excitation with a diffraction grating of 1200 mm-1 as the monochromator to study the vibrational modes of the ceramic. UV-Visible (UV-VIS) absorption spectrometer was used to examine absorption spectra in the reflection geometry in the range of 200-800 nm.

Journal Pre-proof 2.4

Dielectric and Electrical measurements:

For electrical measurement, opposite faces of the pellet samples were electroded with the help of commercially available silver paste and then dried in air atmosphere. Utilizing computer controlled LCR meter (PSM LCR 4NL, Model-1735, UK) and laboratory designed sample holder with furnace electrical measurement was carried out within wide range of frequency and temperature respectively at 1 kHz -1 MHz as well as 30oC to 500oC. 3. Results And Discussion 3.1.

Structural Study

The XRD patterns of lead reducing double perovskite Pb2-xSrxBiVO6(x=0, 0.5, 1, 1.5) at room temperature have been illustrated in Fig.1. It is noticed with increase of Sr+2 contents, there is no remarkable variation in XRD patterns. In view of this, the peaks of different compounds are indexed in different crystal system utilizing commercially available software package POWD [32]. On the basis of minimum standard deviation among experimental data and calculated data monoclinic crystal system were selected for all the investigated samples. As there is no impurity phases are noticed it is confirmed materials are well-crystallized in the optimized temperature. With the proper least square refinement the desirable inter-planar spacing (d) i.e. minimum value of ΣΔd=Σ (dobs-dcal) were recorded. It is also noticed, there is little peak shift towards lower angle with increase of Sr2+ concentration which may be ascribe to contraction of host structure as Pb contents are replaced with Sr+2 [33]. Although minor peak shift is noticed in the studied compounds but position of strongest still invariant which concludes crystal growth completed along (3 1 2) direction [30].The crystallite size of the prepared ceramics calculated using the Scherrer’s equation i.e. Phkl =

kλ , where β1/2 = Full width at half maximum, k is a constant and its value is 0.890, β1/2 cosθ hkl

λ=1.5405Å have been compared in Table 1. An increase in the crystallite size with increased Sr2+

Journal Pre-proof concentrations may be due to the increase of lead vacancy in the A-site cations. This is may be due to reduction of oxygen vacancies created due to evaporation of leads. Usually, oxygen vacancies break larger crystallites into smaller one. As ‘Pb’ contents decreases gradually so concentration of oxygen vacancies decreases as a result particle size increases with rise of ‘Sr’ contents. The rietveld analysis of the compounds has been represented in Fig.2. The fitment parameters and atomic positions of the respective compounds are compared in Table 2-4. It is confirmed from Goodness of Fit parameters of the studied compounds rietveld refinements are well fitted with experimental data. 3.2 Micro-Structural Analysis For surface morphology and phase purity of the samples, SEM micrograph and EDS image of the sintered ceramics Pb2-xSrxBiVO6 (x=0.5, 1, 1.5) are illustrated in Fig.3 and 4 respectively. It is observed SEM image have grains non-uniform shape distributed through ought the surface and strength of non-uniformity decreases with rise of Sr+2 contents. As Pb contents decreases, shape of grains gradually changes from rectangular to nearly circular shape which affects the dielectric and phase transition temperature of the studied samples [34]. The different shape and size of grains are noticed with increase ‘Sr’ contents may be due to different oxygen vacancy percentage. Also it is noted grain size increases with rise of ‘Sr’ this can be ascribe to reduction of oxygen vacancy. This is because oxygen vacancy breaks up larger grains into smaller size. Once again, voids in Pb1.5Sr0.5BiVO6 are prominent this is may be due to evaporation of Pb and Bi at higher temperature sintering whereas in other two compounds there are no such voids. Utilizing intersecting methods, the respective grain size have been calculated and are found to be 1.445, 1.334 and 1.237µm for x= 0.5, 1 and 1.5 respectively. In addition to the above, it is also noticed with increase of Sr2+ contents grain boundaries between adjacent grains becomes more and more prominent as a result probability of leakage current and lossy nature will be higher.

Journal Pre-proof For further phase identification of the present compounds, EDS analysis have been carried out and illustrated in Fig. 4. It is observed there is no other element than Bi, V, Sr and O in the prepared sample with different %age which further affirms compounds are single phase and free from any foreign particle contamination. 3.3 Optical Analysis 3.3.1

Raman Spectroscopy

As per the literature [35-38], octahedral symmetry of free vanadates the different types vibrations in RAMAN spectra are, symmetric stretching1(A1), doubly degenerate anti-symmetric2(E), triply degenerate symmetric bending5 (F2) and lattice vibration mode L(T). Griffith [36] reports, free vanadate possesses symmetric stretching at 877 cm-1, 503 cm-1and double degenerate anti-symmetric stretching mode850 cm-1, 810 cm-1where as bending mode is 228 cm-1. The non-destructive Raman Spectroscopy is quite instrumental in understanding the signature of vibrational frequency in the vanadate based compounds followed by measurement of phase transition temperature and crystallographic orientation in the sample. The strontium based vanadate double perovskite belonging to octahedral tilting system with monoclinic structure of space group P21/n. According to group theory P21/n space group possess 24 vibrational band which can be represented by Г = υ1(Ag + Bg) + υ2(2Ag + 2Bg) + υ5(3Ag + 3Bg) + T(3Ag + 3Bg) + L(3Ag + 3Bg). The room temperature RAMAN spectra of the studied compounds are illustrated in Fig 5 (a-c). In the studied compounds the two formula units of Pb2-xSrxBiVO6 per unit cell which reveals Raman spectra possess all the modes of components Ag and Bg. In single crystal frequency of Ag and Bg are very close for which polarization Raman spectra are necessary to resolve it. If similar situation is arisen in polycrystalline sample i.e. in the studied sample, then it will behave as a single band of symmetric stretching υ1, doublet for asymmetric stretching υ2 and triplet for symmetric bending υ5.

Journal Pre-proof The peak located at 830, 852, 827 cm-1 in Raman spectra of the respective compounds may be ascribed to oxygen symmetric stretching band υ1. In the present samples octahedral VO6 and BiO6 possess symmetric stretching mode of vibration, where cations are stationary and oxygen atoms are moving about the Bi–O–V axis which result strong peaks are seen at 830, 852, 827 cm-1. The medium peak located at 328, 346 and 306 cm-1of respective samples may be ascribed to υ5internal oxygen bending mode of vibration. There exits weak intense peaks related to asymmetric oxygen stretching υ2 but peak splitting cannot be detected without the help of polarization Raman spectra. The peak at 1465 cm−1 in Pb0.5Sr1.5BiVO6 compound is ascribed to SrVO4 scheelite phase which is also noticed in XRD data of the same compound. Very weak AVO4 scheelite peaks are also noticed in the spectra of several other compounds [39]. As in the studied spectra Ag and Bg components are not properly resolved in normal Raman spectroscopy so it expected υ5 mode is triplet degenerated. In few compounds [39] doublet or triplet degeneracy of peaks are clearly visualized as tolerance factor of the groups is unclear whether it is maximum or minimum. This bending mode of vibrations may be due to octahedral symmetric bending of O-Sr-O. The peak located at 286 cm-1 in PbSrBiVO6 can be ascribed as vibrational lattice mode of vibration which is absent in other compounds. Generally in double perovskite P21/n space group possess six vibration modes three each from Ag and Bg component. In the investigated compound one vibrational mode of vibration is visualized and others are not seen, this is may be due to either lowest intense peaks or below the experimental limitation wave numbers. There is an ambiguity for small peak located at 397 cm-1 in PbSrBiVO6which can be assigned as either external vibrational or internal bending mode [39]. The translational lattice modes of vibrations are generally expected to appear in lower wave number range. As discussed above in double perovskite P21/n space group have both Ag as well as Bg components possessing triplet degeneracy of total six modes. There is also another ambiguity regarding the end of vibrational

Journal Pre-proof mode and starting of translational mode. To differentiate these two modes polarization Raman spectroscopy of the sample is essential. Ayala et.al. [40] reports in their study that vibrational lattice mode lies within 190-310 cm-1 and below 190 cm-1 related to translational lattice mode. In the present study neither it is approached polarization Raman spectra nor have data below 200 cm-1 so it is difficult to assign any translational mode of vibration in the first two compound except in Pb0.5Sr1.5BiVO6. The moderate and slightly broad peak located at 587, 562, 516 cm-1 once again can be ascribed to stationary oxygen atoms are vibrating symmetrically about Bi–O–V axes. The other weak peaks present are due to the V-O and Sr-O irrational modes about the main Raman mode of VBi, V-Sr, Sr-Bi bonds. 3.3.2

FTIR Analysis:

FTIR analysis in the investigated compounds is shown in Fig. 6. Kaur [41] reports, ordinarily lattice vibrations are occurred within the wave number range of 850cm-1-400cm-1.The strongest peak located at 759, 777, 661 cm-1of the respective compounds can be ascribed to anti-symmetric stretching mode of the cations VO6 and second strongest peak of the respective compounds at 484, 510, 522 cm-1 may be assigned to symmetric stretching BiO6 about the axis V-O-Bi since octahedral BO6 belongs to higher concentration of charge carriers [42, 43]. In the studied compounds table 2 compares the different modes of vibration for Raman and IR spectra. It is observed Raman active bands are inactive in IR spectra and vice-versa obeying mutual exclusive principle. The comparison of RAMAN and FTIR frequency are illustrated in Table 5. 3.3.3

Ultraviolet-Visible Absorption Spectroscopy

Usually, UV-Vis Spectroscopy is used to determine energy band gap of the materials having semiconducting properties. To study electro-optic behavior of the materials, electrons are excited from valence band to conduction band by striking electromagnetic radiation on the materials. The

Journal Pre-proof part of incident radiation absorbed by the materials to excite electrons and rest is transmitted as well as reflected. The diffuse transmittance (T) of the sample is given by the ratio of Intensity of transmitted radiation (I) to intensity of incident radiation (Io). The amount of radiation absorbed known as absorbance (A) which related with transmittance (T) is given by, A= - log10 (T). Usually, in the visible portion of the spectrum the sample absorbs effectively for which absorbance attending maximum value. UV-Vis absorption spectra of the synthesized compounds within wavelength range 200-700 nm are presented in Fig. 7. It is seen absorbance in the studied samples is strong enough in the absorption band at 300–650 nm which may be due to charge transition between highest occupied 2p orbital of O-2 and lowest empty orbital 3d of vanadium [44]. The absorption band has a blue shift with an increasing substitution ratio of Pb+2 with Sr+2 cations. It is clear from the graphs that all the materials have absorbance maxima within wavelength range of 300 to 380 nm. The absorption in the ceramic based compounds generally depends on size of cations around the anions. In the studied compounds number of Sr atom increases which in turn absorbance increases. The increase in absorbance leads to reduce the energy band gap which favors to increase the semiconducting properties of the Sr modified vanadates. Once again the increase of conducting behavior of the materials may be ascribing to the presence of oxygen vacancies defects etc. From the knowledge of absorption of coefficients of the molecules one can determine energy band gap (Eg), by utilizing Mott and Davis relation; αh= A (h-Eg) n. The symbol α is the absorption coefficient and all others have their usual meaning. The value of ‘n’ for direct allowed band gap is ½ and that for direct forbidden gap is 3/2, for indirect allowed transition n= 2 and for indirect forbidden transition n= 3. With reducing Pb and increasing Sr content, the band gap energy of the prepared ceramics are calculated from (αh) 2 vs. h graph which are found to be 2.61, 2.68

Journal Pre-proof and 2.23 eV for x= 0.5, 1 and 1.5 respectively by linear fitting the curve as represented in the Fig. 7. Increase in Sr content increases the crystallite size along with a decrease in optical band gap energy. The calculated energy band gap of the present sample is effectively useful for photo catalytic devices as like as few TiO2 based perovskite oxide compounds and compared in Table 6. The above UV-Vis spectroscopy study confirms the material can be useful for photovoltaic/solar cell. The proposed photo catalytic mechanism in the present sample can be explained as per the perovskite oxides. Usually the above activity in present double perovskite sample is due to presence of octahedral VO6. As discussed above in the studied sample 2p-orbital of O-2 act as valence band and empty 3d-orbital of V+5 reflects the conduction band. When ultraviolet light irradiated over the powder sample electrons are excited from valence band to conduction band which generates reactive electron-hole pairs to induce oxidation of organic molecules as a result holes are created at valence band. Generally, holes (h+) are strong oxidant on the surface of the studied sample and able to oxidized the adsorbed H2O molecules or hydroxyl ions into OH radicals (H2O or OH– + h+ → ·OH).On the other hand adsorb O2 reacts with electrons to form super oxide ions. These radicals and super oxide ions degrade and decompose the organic molecules [45-48]. 3.3.4 PL-Spectroscopy When an electronic state of the solid gets excited by an external source, after a short span of time, the excited energy is released in the form of light which is known as Luminescence. If the released energy comes under ultraviolet range i.e. short wave length the phenomenon is known as photoluminescence (PL).Based on the nature of electronic transitions which produces luminescence, calcification of PL can be done. Generally in PL a molecule absorb light of wavelength (λ1) then it spontaneously decays to lower energy state of wave length (λ2). Although, λ1>λ2 but in case of resonance emission λ1= λ2.Whether Luminescence band is fluorescence type or phosphorescence type that could be known from average life time of excited state. Depending on

Journal Pre-proof the relative distance between the excited state and the ground state the relative broadness of the emission band may change. PL of a molecular species is different than that of emission from an atomic species. Usually at resonance atomic emission occurs whereas in molecular species, emission occurs at wavelength longer than that of excitation wavelength. The spin multiplicity of a given electronic state decides whether it is a singlet (paired electrons) or a triplet (unpaired electrons).The ground state is normally a singlet state whereas excited states are either singlet or triplets. When a molecule absorbs light an electron is transferred to excited state within time interval

(10-14 10-15) seconds in same spin multiplicity. This excludes a triplet-excited state, as

the final state of electronic absorption is due to the selection rules for electronic transition which directs the spin state should be maintained upon excitation. The photoluminescence spectrum of the studied samples is illustrated in Fig. 8. A number of peaks are observed within the spectral range of 420-530 nm, which are summarized in the graph of the studied samples. PL peak corresponding to the direct band gap, as obtained from UV-Vis spectrum, cannot be observed with respective wave number of the samples. The broad emission peaks are observed for the samples can be attributed as 6P3 → 6S0 transition of Bi3+, which is allowed due to the mixing of the singlet state with the triplet state [49-51]. The other peaks which are observed in present study may be attributed due to oxygen vacancies and defects corresponding to of Bi-Pb, BiSr related bonds behaving like defects due to compressive stress in the matrix of the studied samples. 3.4

Frequency Dependent Dielectric Measurements

Frequency dependent of εr at selected temperatures for the prepared samples are presented in Fig. 9 at some selected temperatures. For dielectric materials, εr is due to the combined effect of different polarization like atomic polarization (Pa); ionic polarization (Pi), dipolar polarization (Pd), space charge (Ps) responding to frequencies at 1015, 1013, 1010 and 102 Hz respectively [26]. Generally, at

Journal Pre-proof frequencies below ∼102 Hz, all four polarizations are responsible for εr, but space charge have no contribution to εr at frequency above 102 Hz. It is seen that there is no significant change in εr above the frequencies 105 Hz. This confirms, space charge polarization plays an important character in dielectric and electrical behaviors of the material. Thus the presence of vanadium and bismuth cations in double perovskite leads to space charge appears more significant in the crystal. Reason behind the presence of space charge in the compounds usually due to evaporated Bi and Pb during sintering at higher temperatures as a result oxygen vacancies is created which introduce oxygen ionic conduction to the system. The other reasons may be the coexistence of tetra and pentavalent vanadium cations which would also create oxygen vacancies to increase space charge polarization. As B-site cations are dominated by vanadium and bismuth, the hopping effect come into the picture and for which tanδ and electrical conductivity increases sufficiently. It is observed from graphs of studied compounds that, the values of εr decrease till ~100 kHz after which it becomes saturated at different temperature which may be due to release of space charge and relaxor nature [55-57]. In addition to this, It is also noticed that in the investigated compounds, values of εr decreases sharply in low frequency region whereas at frequency above ~10 kHz decrease rate becomes slower which may be due to gradual elimination of different types of polarization. The dielectric response of above type can be better understood from Koop’s and MW phenomenological theory. According to theory, dielectric consists of poorly conducting grain walls and good conducting grains [55]. Usually, ceramics containing multi-valence elements like vanadium, iron etc., possess valance fluctuation as majority of charges are electron. As present compounds are combination of Pb, Bi and V based elements, there is a chance of conversion of penta-valence vanadium into tetravalence vanadium due to hopping of electrons between them. This leads to decrease of εr with the rise in frequency but at sufficiently high frequencies hopping of charge carriers between V+5 and V+4 ions at octahedral sites are unable to cope up with the change in an ac electric field as a result

Journal Pre-proof charge carriers like electrons are gathered near grain walls which in turn dielectric constant gets saturated. When frequency increases further, the direction of motion of electrons change rapidly, this obstructs further the electron movement inside the dielectric material and reduces the accumulation of space charge at the grain boundaries. Due to decrease in space charge polarization, a decrease in the values of the dielectric constants is observed in all the samples. It is also observed that the values of εr increases with rise in temperature in the low frequency region whereas at higher frequencies the values are nearly constant. The low frequency dispersion can be contributed by the hopping mechanism of electrons between V+5 and V+4 ions at octahedral sites which is thermally activated. This increase in hopping mechanism produce local displacement of charges in the direction of the applied electric field and it leads to increase in dielectric polarization as a result εr increases with rise in temperature. The variation of εr with temperature at different frequencies of Pb2-xSrxBiVO6 (x= 0.5, 1.0, 1.5) are shown in Fig. 10. It is noticed that in all the compounds value εr increases with rise of temperature which seems to be approaching for a phase transition which may be referred as ferroelectric to paraelectric one. As transition temperature lies much above the experimental limitation temperature, in the studied compounds transition temperatures are invisible. The increase in ɛr with temperature in the studied compounds may be due to the interaction between phonon and electrons which are usually noticed in multi-valance based materials like V, Fe etc. [56, 57]. In the investigated compounds, Pb and Bi usually unstable and evaporates during high temperature sintering which in turn oxygen vacancies are created. This oxygen vacancy results, appearance of space charge polarization [58, 59] in the compounds. Additionally, due to oxygen vacancies penta-valence vanadium converted into tetra valence vanadium ions [60].The increase in εr can also be explained in terms of hopping mechanism of the energetic charge carriers like electrons, along the direction of the applied electric field between V+5-V+4 octahedral positions [61, 62]. Usually the greater values

Journal Pre-proof of εr at low frequencies are due to accumulation of charge carriers near the grain boundary [63]. Once again the value of εr decreases with rise of Sr+2 contents in the studied compounds. As Pb contents reduces the oxygen vacancies during sintering decreases as a result space charge carriers reduces which in turn εr value decreases. 3.5 Polarization Study Usually in ferroelectric materials, polarization (P) and electric field are related non-linearly. As investigated samples are ceramic based so it possess low field dielectric breakdown as a result in P~E hysteresis loop to achieve saturation polarization in the applied range of electric field is quite difficult. Still we have tried to achieve it by changing area and thickness of the sample with the help of fixture arrangement inside the P-E loop tracer. Although, anomaly in dielectric study of the investigated samples are not noticed so P~E hysteresis loop is additional one to confirm the ferroelectricity in the materials. For this purpose hysteresis loop of investigated compounds are carried out at room temperature and illustrated in Fig.11. The hysteresis loop of the samples is not in proper shape which may be due to lossy behavior of the materials. The lossy behavior of the materials is also noticed in SEM images which reveal strong conductive features. The high conductivity of the present material may be basically due to vacancies created by volatile bismuth as well as lead. Because of this the P–E loop of studied compound exhibits a rounded corner [64] with the applied field and will break down at higher field. Compared with the ferroelectric properties of the Pb2BiVO6 [27] the Sr based samples have been significantly improved. The enhancement of ferroelectricity on SrCO3 doping is attributes to the decrease of the oxygen vacancy concentration and the weakening of the defect mobility which contributes to domain pinning. Remnant polarization (i.e., 2Pr) of all the samples at different electric field reflected in Fig. 11. The presence of ferroelectricity in the studied samples could be confirmed from the nature of hysteresis loop.

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4. Conclusion The series of lead reducing poly crystalline ceramics Pb2-xSrxBiVO6 (x=0.5, 1, 1.5) were tailored by solid state reaction route. The monoclinic crystal structures with space group P21/n have been confirmed both from POWD as well as full proof MAUD refinement. Single phase identification and vibrational properties of the investigated samples have been noticed in XRD, RAMAN, FTIR and EDS analysis. The grain distribution and density of the samples analyzed through SEM image which reveals grain growth more or less completed with minimum void which confirms the compounds have more or less leakage behavior. Optical reasoning of the material through Raman and UV-Vis and PL spectroscopy confirms the band gap energy to be feasible for the use of these materials for blue LED based white LEDs as photovoltaic/solar cell devices. The ferroelectric behavior of the compounds have been verified from both dielectric and polarization study. The room temperature εr value of the investigated samples respectively ~400, ~275 and ~350 which can be useful for multi-layer capacitor as well as other energy storage devices. P-E hysteresis loop study reveals room temperature 2Pr values of the studied compounds respectively ~0.72, 064 and 0.58 μC/cm2 which can be useful for FREM devices.

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45. P. Kanhere, and Z. Chen, A Review on Visible Light Active Perovskite-Based Photocatalysts, Molecules, 19 (2014) 19995-20022. 46. B. Han, Y. Li, N. Chen, D. Deng, X. Xing and Y. Wang, Preparation and Photocatalytic Properties of LnBaCo2O5+δ (Ln = Eu, Gd, and Sm), Journal of Materials Science and Chemical Engineering,3(2015) 17-25. 47. P.Junploy,S.Thongtem and T.Thongtem, Photoabsorption and Photocatalysis of SrSnO3 Produced by a Cyclic Microwave Radiation. Superlattices and Microstructures, 57(2013)110. 48. S.S.Fu, H.L.Niu, Z.Y.Tao, J.M.Song, C.J.Mao,S.Y.Zhang,C.L.Chen and D.Wang, Low Temperature Synthesis and Photocatalytic Property of Perovskite-Type LaCoO3 Hollow Spheres. Journal of Alloys and Compounds, 576(2013) 5-12.

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response of ferroelectromagneticPb(Fe1/2Nb1/2)O3 ceramics obtained by

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Here on behave of authors, I declare that manuscript has not been submitted and acknowledge to the entire researcher directly or indirectly involved in the research article. There not associated with any type of conflict of interest in this manuscript. Dr. B N Parida

INTENSITY (ARB.UNIT)

(841) (048)

(360) (629)

(626) (607)

(217) (242)

(034)

(406) (116)

(122)

(123) (030)

x=1.5 (016)

(010) (211)

(312)

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x=1

x=0.5

x=0

20 25 30 35 40 45 50 55 60 65 70 75 80

BRAGG'S ANGLE (2) Fig. 1: Room temperature powder XRD patterns of Pb2-xSrxBiVO6 (x=0.5, 1, 1.5).

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X=0.5

(a)

Intensity (Arb. Unit)

Expt Cal Bkg

20 (b)

30

40 50 60 Bragg Angle(2)

40 50 60 Bragg Angle(2)

70

X=1.5

Intensity (Arb. Unit)

Intensity (Arb.Unit)

30

80

(c)

X=1 Expt Cal Bkg

20

70

80

20

30

40 50 60 Bragg Angle(2)

Fig. 2(a-c) reflects the reitveld fit for experimental data of Pb2-xSrxBiVO6 (x=0.5, 1&1.5)

Expt Cal Bkg

70

80

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X=0.5

X=1.0 Fig.3 reflects the SEM image of the studied samples Pb2-xSrxBiVO6

X=1.5

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x=0.5

x=1.0

x=1.5

Fig.4 reflects the EDX Spectra of the studied samples Pb1-xSrxBiVO6 9x=0.5, 1.0 & 1.5)

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x=1

666

852

830

(b)

x=0.5

1000 1500 -12000 RAMAN Shift (cm )

562

346

500

2500 827

(c)

1000 1500 2000 -1 RAMAN shift( cm )

x=1.5

500

1463

511

306

Intensity (Arb. Unit)

500

397

589

Intensity (Arb.Unit)

328

Intensity ( Arb. Unit)

(a)

1000 1500 -1 2000 RAMAN Shift (cm )

2500

2500

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Fig. 5 (a-c) illustrates the room temperature RAMAN Spectra of Pb2-xSrxBiVO6 for x=0.5, x=1 and x= 1.5.

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759

20 0 3000 2250 1500 -1 Wave number(cm ) 150

750 (c)

408

1019

Pb0.5Sr1.55BiVO6

30

864 661 522 427 1528

90 60

0 3750

510

3000 2000 1000 -1 Wave number(cm )

120 3667

3750

PbSrBiVO6

777

40

404 484

60

Intensity(Arb.unit)

80

Intensity(Arb.unit)

Intensity(Arb.unit)

100

160 (b) 140 120 100 80 60 40 20 0 -20 4000

1698 1561

Pb1.5Sr0.5BiVO6

2889

(a)

983

120

3000 2250 1500 -1 Wave number(cm )

750

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Fig 6 (a-c) illustrates FTIR spectra of the studied samples.

UV Range

20 15 10 5

Eg=2.61eV

0

Absorbance

700

1

3

4 h(eV)

6

7

10 5 Eg=2.68eV

0

Visible Range

300 400 500 600 WAVELENGTH ()(nm)

5

15

2(eV/cm)2 UV Range

2 PbSrBiVO6

(h)

ABSORPTION

Absorbance

1

700

35

Pb0.5Sr1.5BiVO6 Absorbance

2

3

4 5 h(eV)

6

7

Pb0.5Sr1.5BiVO6

30

2

25

2

( h) (eV/cm)

ABSORPTION BSORPTION

300 400 500 600 WAVELENGTH ()(nm)

Pb1.5Sr0.5BiVO6

25

PbSrBiVO6

20 15 10 5

UV Range

200 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5

Visible Range

Absorbance

200

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

2(eV/cm)2

Absorbance

200

1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

30

Pb1.5Sr0.5BiVO6

(h)

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

Visible Range

Eg=2.23eV

0

300 400 500 600 WAVELENGTH ()(nm)

Absorbance

-5

700

1

Sr2BiVO6 Absorbance

)2(eV/cm)2

ABSORPTION

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65 60 55 50 45 40 35 30 25 20

2

3

4 h(eV)

Sr2BiVO6

5

6

7

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Fig.7 illustrate UV-VIS Spectra of Pb2-xSrxBiVO6 (a) x=0.5, (b) x=1 and (c) x= 1.5 at room temperature.

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Pb1-xSrxBiVO6

451

ex=400 nm

200

483

150

492

428

Intensity (Arb. unit)

250

429 428

300

100

360

380

400 420 440 460 Wavelength (nm)

480

x=1.5, Eg=2.92 eV, FWHM=105 nm x=1, Eg=2.90 eV, FWHM=90 nm x=0.5, Eg=2.92 eV, FWHM=123 nm

Fig. 8 illustrates PL spectra of the studied compounds.

500

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2000 Pb1.5Sr0.5BiVO6

PbSrBiVO6

0

r

1500

1000

0

350 C 0 375 C 0 400 C 0 425 C 0 450 C

450 400 r

400 C 0 425 C 0 450 C 0 475 C 0 500 C Fit

350 300

500 1

10 100 Frequency(kHz)

1000

10000

250 2

3

10

10

4

5

6

10 10 10 Frequency(kHz)

7

10

900 Pb0.5Sr1.5BiVO6

800

r

700 600

0

375 C 0 400 C 0 425 C 0 450 C 0 475 C 0 500 C Fit

500 400 300 1

10 100 1000 Frequency (kHz)

10000

Fig.9 represents frequency dependence relative permittivity of Pb2-xSrxBiVO6 forx=0.5, 1 and 1.5.

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1400 1 kHz 10 kHz 100 kHz

1000

Pb1.5Sr0.5BiVO6

600

1200

800

r

r

1000

1kHz 10 kHz 100 kHz

800

600

PbSrBiVO6

400

400 100

200 300 400 0 Temperature( C)

500

200 0

100

700 1kHz 10kHz 100kHz

600

r

0

500 Pb0.5Sr1.5BiVO6 400 300 0

100 200 300o 400 Temperature ( C)

500

200 300 0 400 Temperature( C)

500

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Fig. 10 illustrates the temperature dependent of dielectric constant at different frequencies of the studied samples.

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1.50

Pb1.5Sr0.5BiVO6 2

2

P (  C/cm 2)

0.75 2Pr=0.72C/cm P (  C/cm 2)

PbSrBiVO6

1.50

0.00

-0.75

0.75

2Pr=0.64C/cm

0.00

-0.75

-1.50

-1.50

-2.25 -0.5

0.0 0.5 1.0 E(kV/cm) 1.50 Pb0.5Sr1.5BiVO6

-1.0

0.75 2P =0.58C/cm2 r P (  C/cm 2)

-1.0

0.00

-0.75 -1.50 -1.0

-0.5

0.0 0.5 E(kV/cm)

1.0

-0.5

0.0 0.5 E(kV/cm)

1.0

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Fig. 11 represents the room temperature PE hysteresis loop of the studied samples.

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Highlights 

The material is ‘Sr’ doped lead reducing double perovskite prepared by inexpensive solid solution casting method.



Structural and micro structural study reveals single phase, high symmetry and highly dense compound.



Dielectric and polarization study infers it can be useful for multilayer capacitor and memory devices.



Optical properties of the material reflect it can be useful for photovoltaic/solar cell and blue white LED devices.

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Table 1: Comparison of Crystal structure, Lattice parameters and crystallite size of the studied samples

Crystal Structure

Cell Parameters a (Å) b (Å) c (Å)

Sl.No.

Samples Pb2-xSrxBiVO6

1

x=0.5

Monoclinic

7.4543

6.0265

28.3345

45

2

x=1

Monoclinic

7.4121

6.2054

28.4963

61

3

x=1.5

Monoclinic

7.8531

5.9742

28.4524

69

Crystallite Size (nm)

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Table 2 compares the different parameters and Atomic position of Pb1.5Sr0.5BiVO6. GOF= (Chi)2 = 1.85, Rwp (%) = 29.22, Rexp(%) = 13.53, RB (%) = 25.68 Unit Cell: a=7.32 Å, b=5.44 Å, c=28.37 Å, α=90.0, β=94.27 , θ=90.0, Volume: V=1308.53Å3 Space group: P 21/ n Crystal System: Monoclinic Atom Bi Bi Bi Bi Pb Pb Pb Pb Pb Pb Sr Sr V V V V O O O O O O O O O O O O O O O O O O O O O O O O

# 1 2 3 4 1 2 3 4 5 6 7 8 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

OX 3.0 3.0 3.0 3.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 5.0 5.0 5.0 5.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0

SITE 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a

X 0.074(2) 0.816(2) 0.616(2) 0.401(2) 0.588(2) 0.803(2) 0.867(2) 0.117(2) 0.182(3) 1.007(3) 0.928(3) 0.260(3) 0.351(2) 0.174(2) 0.028(3) 0.335(2) 0.40545 0.16801 0.31289 0.52053 0.10038 0.06031 0.14523 0.39184 0.09583 -.19428 0.12143 0.08951 0.32443 0.37136 0.50226 0.14235 0.385(3) 0.327(4) 0.344(4) 0.176(4) 0.023(4) 0.370(4) 0.047(3) 0.160(3)

Y 0.501(3) -.007(2) 0.004(3) 0.488(2) 0.026(3) 0.484(2) 0.044(2) 0.477(3) -.012(2) 0.511(3) 0.463(2) -.027(3) 1.056(2) 0.027(2) -.490(2) 0.510(2) 1.25862 1.14238 0.79945 1.02655 -.08889 -.08617 0.31922 -.03279 -.62214 -.46337 -.22372 -.65251 0.26055 0.73639 0.49261 0.55131 0.190(4) 0.732(5) 0.276(4) 0.217(5) 0.728(5) 0.765(5) 0.233(4) 0.704(4)

Z 0.2010(6) 0.1582(6) 0.8975(6) 0.4470(4) 0.3747(7) 0.8201(7) 0.2781(6) 0.7295(6) 0.5190(7) 0.07584(7) 0.4737(7) 0.1284(7) 0.2388(6) 0.0035(6) 0.6000(7) 0.8573(7) 0.19935 0.26421 0.21142 0.28042 0.0527 -.04402 0.00419 0.00145 0.6512 0.59636 0.59811 0.55468 0.88836 0.8947 0.82161 0.82483 0.721(1) 0.718(1) 0.376(1) 0.457(1) 0.137(1) 0.384(1) 0.142(1) 0.468(1)

SOF 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

H 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

ITF(B) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9)

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Table 3 compares the different parameters and Atomic position of PbSrBiVO6. GOF= (Chi) 2 = 1.84, Rwp (%) = 29.37, Rexp(%) = 12.48, RB (%) = 24.065 Unit Cell: a=7.53 Å, b=5.55 Å, c=28.24 Å, α=90.0, β=94.27 , θ=90.0, Volume: V=1308.53Å3 Space group: P 21/ n Crystal System: Monoclinic Atom Bi Bi Bi Bi Pb Pb Pb Pb Sr Sr Sr Sr V V V V O O O O O O O O O O O O O O O O O O O O O O O O

# 1 2 3 4 1 2 3 4 5 6 7 8 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

OX 3.0 3.0 3.0 3.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 5.0 5.0 5.0 5.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0

Site 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a

X 0.074(2) 0.816(2) 0.616(2) 0.401(2) 0.588(2) 0.803(2) 0.867(2) 0.117(2) 0.182(3) 1.007(3) 0.928(3) 0.260(3) 0.351(2) 0.174(2) 0.028(3) 0.335(2) 0.40545 0.16801 0.31289 0.52053 0.10038 0.06031 0.14523 0.39184 0.09583 -.19428 0.12143 0.08951 0.32443 0.37136 0.50226 0.14235 0.385(3) 0.327(4) 0.344(4) 0.176(4) 0.023(4) 0.370(4) 0.047(3) 0.160(3)

Y 0.501(3) -.007(2) 0.004(3) 0.488(2) 0.026(3) 0.484(2) 0.044(2) 0.477(3) -.012(2) 0.511(3) 0.463(2) -.027(3) 1.056(2) 0.027(2) -.490(2) 0.510(2) 1.25862 1.14238 0.79945 1.02655 -.08889 -.08617 0.31922 -.03279 -.62214 -.46337 -.22372 -.65251 0.26055 0.73639 0.49261 0.55131 0.190(4) 0.732(5) 0.276(4) 0.217(5) 0.728(5) 0.765(5) 0.233(4) 0.704(4)

Z 0.2010(6) 0.1582(6) 0.8975(6) 0.4470(4) 0.3747(7) 0.8201(7) 0.2781(6) 0.7295(6) 0.5190(7) 0.07584(7) 0.4737(7) 0.1284(7) 0.2388(6) 0.0035(6) 0.6000(7) 0.8573(7) 0.19935 0.26421 0.21142 0.28042 0.0527 -.04402 0.00419 0.00145 0.6512 0.59636 0.59811 0.55468 0.88836 0.8947 0.82161 0.82483 0.721(1) 0.718(1) 0.376(1) 0.457(1) 0.137(1) 0.384(1) 0.142(1) 0.468(1)

Table 4 compares the different parameters and Atomic position of Pb0.5Sr1.5BiVO6.

SOF 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

H 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

ITF(B) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9)

Journal Pre-proof

GOF= (Chi) 2 = 1.65, Rwp (%) = 29.57, Rexp(%) = 12.38, RB (%) = 30.94 Unit Cell: a=7.32 Å, b=5.49 Å, c=28.27 Å, α=90.0, β=94.27 , θ=90.0, Volume: V=1308.53Å3 Space group: P 21/ n Crystal System: Monoclinic Atom Bi Bi Bi Bi Pb Pb Sr Sr Sr Sr Sr Sr V V V V O O O O O O O O O O O O O O O O O O O O O O O O

# 1 2 3 4 1 2 3 4 5 6 7 8 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

OX 3.0 3.0 3.0 3.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 5.0 5.0 5.0 5.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0 -2.0

SITE 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a

X 0.074(2) 0.816(2) 0.616(2) 0.401(2) 0.588(2) 0.803(2) 0.867(2) 0.117(2) 0.182(3) 1.007(3) 0.928(3) 0.260(3) 0.351(2) 0.174(2) 0.028(3) 0.335(2) 0.40545 0.16801 0.31289 0.52053 0.10038 0.06031 0.14523 0.39184 0.09583 -.19428 0.12143 0.08951 0.32443 0.37136 0.50226 0.14235 0.385(3) 0.327(4) 0.344(4) 0.176(4) 0.023(4) 0.370(4) 0.047(3) 0.160(3)

Y 0.501(3) -.007(2) 0.004(3) 0.488(2) 0.026(3) 0.484(2) 0.044(2) 0.477(3) -.012(2) 0.511(3) 0.463(2) -.027(3) 1.056(2) 0.027(2) -.490(2) 0.510(2) 1.25862 1.14238 0.79945 1.02655 -.08889 -.08617 0.31922 -.03279 -.62214 -.46337 -.22372 -.65251 0.26055 0.73639 0.49261 0.55131 0.190(4) 0.732(5) 0.276(4) 0.217(5) 0.728(5) 0.765(5) 0.233(4) 0.704(4)

Z 0.2010(6) 0.1582(6) 0.8975(6) 0.4470(4) 0.3747(7) 0.8201(7) 0.2781(6) 0.7295(6) 0.5190(7) 0.07584(7) 0.4737(7) 0.1284(7) 0.2388(6) 0.0035(6) 0.6000(7) 0.8573(7) 0.19935 0.26421 0.21142 0.28042 0.0527 -.04402 0.00419 0.00145 0.6512 0.59636 0.59811 0.55468 0.88836 0.8947 0.82161 0.82483 0.721(1) 0.718(1) 0.376(1) 0.457(1) 0.137(1) 0.384(1) 0.142(1) 0.468(1)

SOF 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

H 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

ITF(B) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.18(5) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.68(8) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9) 1.38(9)

Journal Pre-proof

Table 5 compares the RAMAN and FTIR Peaks for different modes of vibration. Pb1.5Sr0.5Bi PbSrBi Pb0.5Sr0.5Bi VO6 VO6 VO6 RAMAN Shift in cm-1 --286

328

347

306

----

---

---

----

393

587 --

562 664

516

832

853

827

Modes of Vibration

Pb1.5Sr0.5B PbSrBi Pb0.5Sr0.5Bi iVO6 VO6 VO6 FTIR Peaks in cm-1

Libration al Lattice mode

404

408

427

Antisymmetri c bending vibration of Bi-OV external librationa l or internal bending mode Irrational mode

484

510

522

--759

--777

661 864

---

1019

983

-----

1561 1698

1528 ---

---

2889

---

symmetri c stretchin g vibration of Bi-OV oxygen symmetri c stretchin g

Modes of Vibration symmetri c stretchin g antisymmetri c stretchin g symmetri c and asymmet ric bending mode of vibration s for OV-O symmetri c and asymmet ric stretchin g vibration of O-SrO defect vibration

Journal Pre-proof

Table 6 compare the energy band gap (Eg) as well as photo catalytic activity of the present compound with other perovskite based compounds.

Name of the compounds

Egin eV

Photo Catalytic activity

CoTiO3 NiTiO3 FeTiO3 CdTiO3 PbTiO3 AgTaO3 KTaO3 AgVO3

2.28 2.16 2.8 2.8 2.75 3.4 3.6 2.3-2.5

Present

[39]

Present

[40]

LnBaCo2O5+δ (Ln = Eu, Gd, and Sm)

Present compound Pb1.5Sr0.5BiVO6 Present compound PbSrBiVO6 Present compound Pb0.5Sr1.5BiVO6

2.61 2.68 2.23

May show the Photo Catalytic activity

Reference