Bismuth-substituted hydroxyapatite ceramics synthesis: Morphological, structural, vibrational and dielectric properties

Journal Pre-proof Bismuth-substituted hydroxyapatite ceramics synthesis: Morphological, structural, vibrational and dielectric properties

Asmaa El Khouri, Abdelouahad Zegzouti, Mohamed Elaatmani, Francesco Capitelli PII:

S1387-7003(19)30560-X

DOI:

https://doi.org/10.1016/j.inoche.2019.107568

Reference:

INOCHE 107568

To appear in:

Inorganic Chemistry Communications

Received date:

1 June 2019

Revised date:

20 August 2019

Accepted date:

4 September 2019

Please cite this article as: A. El Khouri, A. Zegzouti, M. Elaatmani, et al., Bismuthsubstituted hydroxyapatite ceramics synthesis: Morphological, structural, vibrational and dielectric properties, Inorganic Chemistry Communications (2019), https://doi.org/ 10.1016/j.inoche.2019.107568

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© 2019 Published by Elsevier.

Journal Pre-proof

Bismuth-substituted hydroxyapatite ceramics synthesis: morphological, structural, vibrational and dielectric properties Asmaa El Khouri a,*, Abdelouahad Zegzouti a,Mohamed Elaatmani a, Francesco Capitelli b a

Laboratoire Sciences des Matériaux Inorganiques et leurs Applications, Faculté des Sciences Semlalia, BP 2390, Université Cadi Ayyad, Marrakech, Morocco

b

Istituto di Cristallografia – CNR, Via Salaria Km 29.300, 00016 Monterotondo (Rome), Italy

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*Corresponding author. Tel. +212615194963 E-mail address: [email protected]

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Abstract

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New hydroxyapatite (HAp) ceramics substituted with 10, 30 and 50 at.% of bismuth were synthesized by conventional solid state reaction at high temperature T=1300°C, and

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characterized via X-ray diffraction, scanning electron microscopy, Fourier transform infrared

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and Raman spectroscopies; dielectric properties were also investigated. The hydroxyl groups observed in infrared spectra confirmed the HAp phase in the studied samples. The crystallite size

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was estimated by Scherrer’s formula and the Williamson–Hall plot, while lattice parameters and the unit cell volume of the samples were measured according to Bi content.Scanning electron microscope images revealed the presence of grains with irregular sizes developed within larger

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aggregations. Measured relative dielectric permittivity and dielectric loss are slightly affected by Bi content, while the alternating current conductivity increases with a rise frequency, and decreases at increasing of Bi content. The HAp-Bi50% sample presents the optimal dielectric properties.

Keywords: Hydroxyapatite; Bismuth; Solid state reaction; Microstructure, Vibrational and Dielectrical properties.

1

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1. Introduction Hydroxyapatite (HAp) Ca10(PO4)6(OH)2 is one of the most common forms of calcium phosphate compounds, being one of the three end-members of the apatite family within the ideal formula Ca10(PO4)6(F,Cl,OH)2:

differently

from

fluorapatite

Ca10(PO4)6F2

and

chloroapatite

Ca10(PO4)6Cl2, HAp contains hydroxide ions (OH)-, widely recognized as the source of its interesting properties, making it useful in various applications[1-3]. For example, due to its similarity in chemical composition to the mineral phase of bone tissues and teeth, it is widely applied in medicine as synthetic bone substitutes and in the coating of metallic implants [4].

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Moreover, HAp was studied as a material for fuel cell and fluorescent lamps [5-6], or as

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adsorbent of toxic substances in liquid or gas [7-8], also used in gas sensors [9], and mercury

several publications and patents [11- 13].

-p

tubes [10], others catalytic and antimicrobial activities of hydroxyapatite are a subject matter of

On the other side, since bone is a dielectric material, the electric and dielectric properties of HAp

re

ceramics have recently received significant attention due to their role in enhancing biological

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response [14].Furthermore, the effects of the electrical stimulation and electromagnetism for bone healing have been reported [15–17].

Generally, compounds containing bismuth have significant medical applications as antibacterial

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and anticancer agents [18],while bismuth-containing pharmaceuticals have been used as medicine for gastrointestinal disorders and syphilis pathologies, and owing to their radio-opacity

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properties it was also added to various bone and dental implants [19–20].Bismuth element with the oxidation number Bi3+ is considered to be the only relevant bismuth species in biological systems [21], and it considered slightly toxic to humans because of their low uptake into human cells[22].

However, the most important feature of HAp structure is the ability to form a set of solid solutions by accepting a large number of anionic and cationic substituent [3]. Thus, information about dopant location in the apatite structure is important for formulating a synthetic hydroxyapatite having some specified properties. Hydroxyapatites substituted by trivalent elements are less frequent, and there is only limited information on this type of isomorphous substitution and resultant modification [3]: in particular, about Ca-Bi system, despite some studies devoted to synthetic calcium phosphates doped with bismuth ion [23-24], to date on structural studies of Bi-replaced HAp we quote only [25].

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Journal Pre-proof Thus, in the present work we present a facile synthesis route by means of solid state reaction of new bismuth-substituted hydroxyapatite solid solutions, within the context of our recent investigations on calcium phosphate materials [26-27]. The effects of the calcium substitution by bismuth in HAp lattice on structural, vibrational, and dielectrical properties were investigated by means of multi-methodological approach based on scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and Raman spectroscopies, and discussed in this paper.

2. Experimental

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Bismuth substituted hydroxyapatite based samples were synthesized by solid state route for the various molar ratios of Bi/(Ca + Bi):0, 0.01,0.03and 0.05. Stoichiometric amounts of

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CaCO3(Fluka 99%), CaHPO4(Prolabo  97%), and Bi2O3(Rectapur 99%) were mixed using

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Agate mortar and pestle for 1 hour. The homogenized powders were then placed in alumina crucibles and calcined at high temperature (T=1300°C) for 7 h. For the dielectric measurements,

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prepared powders were ground, mixed, and pressed by uniaxial pressure to form pellets with a 13 mm diameter and varying thickness(0.8
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temperature and time. Samples were prepared according to the following reactions:

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4CaCO3 + 6CaHPO4 → Ca10(PO4)6(OH)2+ 4CO2 + 2H2O

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3.85CaCO3 + 6CaHPO4+0.05Bi2O3 → Ca9.85 Bi0.1(PO4)6(OH)2 +3.85CO2 +2H2O

(2)

3.55CaCO3 + 6CaHPO4+0.15Bi2O3 → Ca9.55 Bi0.3(PO4)6(OH)2 +3.55CO2 +2H2O

(3)

3.25CaCO3 + 6CaHPO4+0.25Bi2O3 → Ca9.25 Bi0.5(PO4)6(OH)2 +3.25CO2 +2H2O

(4)

The obtained synthesized phases are typed in bold, but in hence in the manuscript they will be reported, for the sake of clarity, as Ca10(PO4)6(OH)2=HAp, Ca9.85Bi0.10(PO4)6(OH)2= HAp10%Bi, Ca9.55Bi0.30(PO4)6(OH)2= HAp-30%Bi and Ca9.25Bi0.50(PO4)6(OH)2= HAp-50%Bi, respectively. The powder diffraction data of synthesized samples were recorded at room temperature using Bruker Binary V3 diffractometer with the Cu Kα radiation (λKα = 1.54056 Å) and equipped with an LYNXEYE detector. The spectra were measured in the angular range 10–60° (2θ), with a step size of 0.04° (2θ) and a data collection time of 10 min.The measures were executed in Bragg-Brentano geometry. 3

Journal Pre-proof Detailed morphological analyses were performed using a TESCAN VEGA3 scanning electron microscope (SEM), with a maximum voltage of 10 kV. Samples were placed on stab and pressed then coated with carbon to be exposed to the electron beam. FTIR spectra of the samples were collected from the VERTEX 70 FTIR spectrometer over the range of 400-4000 cm-1and equipped with a DTGS detector; the nominal resolution was 4 cm−1 and 64 scans were averaged for both sample and background. The samples were prepared using the KBr pellet technique. Raman spectra on powders were obtained by using a compact Raman confocal microscope confotec

TM

MR520 with a high sensitivity and spatial resolution, equipped with PMT detectors

and CCD camera for spectral measurements with Peltier cooling.The laser source was a He-Ne

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laser at λ = 532 nm.

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The dielectric measurements were performed at room temperature and from 1 Hz to 1 MHz, using Solartron 1296A, at Ac 100 mV.The ceramics were coated with a silver anchor on both

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sides to form the electrodes

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3. Results and discussion

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3.1. XRD results

Hydroxyapatite crystallize usually in the hexagonal system, space group P63/m, with the

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following crystallographic parameters: a = b = 9.418 Å, c = 6.881 Å, =  = 90°, =120°(JCPDS No. 9-432) [28]. HAp structure can be described as a compact assemblage of irregular Ca(1)O9

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polyhedra and Ca(2)O6OH distorted pentagonal bipyramidal groups, joined by quite regular PO4tetrahedral groups[28-29].

X-ray diffraction technique was used to determine the unit cell parameters of Bi-substituted HAp solid solutions. The obtained X-ray diffraction patterns are shown in Fig.1, while unit cell parameters of prepared samples are reported in Table 1.

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HAp:50%Bi

HAp

TCP

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HAp:10%Bi

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Intensity (a.u)

HAp:30%Bi

re

-p

HAp

20

30

40

50

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Wavenumbers (cm-1)

na

Fig. 1: X-Ray patterns of HAp-Bi solid solutions

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Theoretical values of the density of HAp phases were calculated using equation (5): MZ

 = NAV

(5)

where M is molecular weight of phase, molecular unit cell Z = 2, NA is Avogadro’s number, V is volume of the phase. The experimental values of density of prepared phases were estimated by equation (6). M3−M1

 = (M2−M1)−(M4−M3) dsolvent

(6)

Where, dsolvent= Diethyl phthalate (C12H14O4), d=1.118, M1=mass of dry pycnometer,M2=mass of pycnometer filled with solvent, M3= mass of pycnometer with ceramic, and M4 = mass of pycnometer with ceramic and solvent.The theoretical and experimental values of density (Table 1 and Fig 2) are consistent and in good agreement with literature [30].

5

Journal Pre-proof The substitution of Bi, whose ionic radius (1.17 Å) is close to calcium one (1.00Å),causes slight modifications in cell parameters, a=b, c and Volume (Table 1, Fig.3).When compared to undoped HAp sample, the strongest HAp plane was shifted to smaller angles of 2Ɵ for Bi doped apatite phases. This indicates the incorporation of Bi into HAp structure. According to previous reports [30-33], the substitution of ions in HAp structure depends on the strength of the bonds between the ions and the surrounding atoms, the charge of the cations, and nature of the anions present in the ion channel [34]. In general the Ca (1) site is smaller in volume than the Ca (2) site [35]. This does not imply that larger ions prefer the Ca (2) site for substitution. The Ca(1) site can guest large ions, because of its longer ion-oxygen bond distance. With the augmentation of substituted ions in Ca(1), the’c’ axis becomes elongated due to the mutual repulsion, which gets

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partially restrained by the insertion of ions at the Ca(2) site [36]. Furthermore, with the addition

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of over50% Bi, the decomposition of HAp in α-Ca3(PO4)2(α-TCP) and CaO was identified according to the reaction (7), in good agreement with results obtained by other authors [24, 37-

-p

38].

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Ca(20−3x)/2Bix (PO4)6 (OH)2 →α-Ca(3−3x/2)Bix( PO4)2+ CaO + H2O

(7)

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The average crystallite size (Table 2) was estimated from the PXRD peaks using Debye-Scherer

na

Formula (equation 8), and William-Hall relation (equation 9).

𝑑=

kλ β𝑐𝑜𝑠𝜃

(8)

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Where β is the full-width half-maximum value of the high intensity peak, θ is the angle at which the maximum peak occurs, k is the so-called shape factor, and λ is the wavelength of the X-ray source used in the XRD (λ copper=1.541Å). βℎ𝑘𝑙 𝑐𝑜𝑠Ɵ =

k 𝑑

+ 4sinƟ

(9)

As indicated in Table 2, the crystallite size decreased noticeably with the increase of bismuth concentration (Fig 4).Moreover, according to previous reports, it is expected that trivalent ions incorporation in apatite structure can lead to a size reduction of crystallites [24,39-41]. In Debye Scherrer method the crystallite size varied from 77.68 nm for HAp, to 69.81nm for HAp-Bi50%; a plot of 1/β on the x-axis and cosƟ along they-axis for the prepared phases was given in Fig.5.

6

Journal Pre-proof A similar behavior was observed in the Williamson–Hall method, where the strain (ε) and crystallite size (d) are determined from the slope and the βcosθ -intercept of 4sinθ vs. βcosθ (Fig. 6). The strain values vary from 3.24 × 10–3, for pure Hap,to 3.29 × 10–3, for HAp- Bi50%.The average crystallite size was 85.92 nm, 79.93 nm, 76.36 nm, and 66.63nm for HAp, HAp-10%Bi, HAp-30%Bi,and HAp-50%Bi, respectively.

Table 1: Crystal parameters of Bi-HAp phases.

(Ca+Bi)/ P

V ( nm3)

Lattice parameters (nm) a  0.0002

b  0.0002

c  0.0003

 0.0229 52.794 52.782

Lattice Distortion c/a

Density g/cm3 Experimental

Theoretical

0.7306

3.186

3.160

0.7307

3.251

3.207

of

Sample

1.66

0.9413

0.9413

0.6878

HAp 10%

1.65

0.9412

0.9412

0.6878

HAp 30%

1.64

0.9413

0.9413

0.6877

52.778

0.7306

3.309

3.300

HAp 50%

1.62

0.9412

0.9412

0.6878

52.769

0.7307

3.354

3.395

na

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-p

ro

HAp

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Table 2: Crystallites size of Bi-HAp phases. Crystallite size D(nm)

Sample

HAp HAp 10% HAp 30% HAp 50%

Debye-Scherrer method 77.68 75.51 74.16 69.81

Williamson- Hall method D(nm) 10-3 85.92 3.24 79.93 3.13 76.36 66.63

2.17 3.29

7

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Theoretical density Experimental density

3.40

Debye-Scherrer Williamson- Hall

Crystallite size D( mm)

3 Density (g/cm )

3.35 3.30 3.25 3.20 3.15 0.1

0.2

0.3

0.4

0.0

0.5

0.1

0.2

0.3

0.4

0.5

Concentration X

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0.0

Concentration X

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Fig.4. Variation of crystallite size of HAp-Bi compositions

0.0

0.1

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0.2

0.3

0.4

Concentration X

Fig.3. Trend of volume of HAp-Bi compositions

0.96185

HAp-50%Bi

0.96180

y = -4E-06x + 0.963 R² = 0.903

0.96175 0.96170

Cos 

na

-3 Volume/ 10 nm

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Cell volume

re

-p

Fig.2. Theoretical and experimental values of density HAp-Bi compositions

HAp-10%Bi

0.96165

HAp-30%Bi

0.96160

HAp

0.96155 0.96150 0.5

470

480

490

500

510

520

1/ Fig.5. Scherrer plot of HAp-Bi compositions

8

530

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0.0040

0.0026

HAp-Bi10%

HAp 0.0024

0.0035

0.0022 0.0020

Cos 

cos 

0.0030

0.0025

0.0020

0.0018 0.0016 0.0014

y = 0.003249469447x - 0.00161130618 R² = 0.999 1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

y = 0.003130068577x - 0.00173477528 R² = 0.988

0.0012 0.0010 0.95

1.8

1.00

1.05

1.10

1.15

1.20

4 sin 

1.25

1.30

1.35

1.40

0.0030

-p

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4 sin 

of

0.0015

0.0040

0.0035

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0.0024 0.0021

na

0.0018 0.0015 0.0012 1.1

1.2

1.3

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y = 0.002174815912x - 0.00181842697 R² = 0.943 1.4

1.5

4 sin 

1.6

1.7

1.8

0.0030

 cos 

0.0027

cos

HAp-Bi50%

re

HAp-Bi30%

0.0025

0.0020

y = 0.003295815537x - 0.00208764045 R² = 0.993

0.0015 1.0

1.2

1.4

1.6

1.8

4 sin

Fig.6. W-H analysis of HAp-Bi compositions, the strain is extracted from the slope and the crystalline size is extracted from the y-intercept of the fit.

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Journal Pre-proof 3.2. Microstructure analysis Despite the morphological investigation of apatite specimens via scanning electron microscopy (SEM) has been presented by several authors [42-43, 2], morphological data of Bi substituted HAp samples are missing in the literature. The SEM images at 10 μm of synthesized powders and ceramics are shown in Figs. 7-8. Fig. 7 depicts micrographs of pure and Bi substituted HAp powders exhibiting randomly distributed grains with variable size and shape, and the grains have been highly merged by the effect of synthesis temperature, and the results are in accordance with published results [44,31]. Fig. 8 shows the morphology of pure and Bi substituted HAp ceramics, wherein the grains are found to agglomerate among each other to form plate-like structure, due

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to the influence of applied pressure and treatment temperature of ceramics. At higher

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concentration of HAp-Bi50%, smaller grains agglomerated tightly into aggregates, which are observed covering the whole surface. It is clearly seen that the gradual addition of Bi ions results

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in trapping the HAp crystallites in to smaller grains, causing an increase in micro-pores and then

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an increase of the active surface area. This feature affects adsorption properties of HAp samples.

Fig. 7: SEM image taken at 10µm of HAp-Bi powders

10

re

-p

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Fig. 8: SEM image taken at 10µm of HAp-Bi ceramics

3.3. Vibrational spectroscopy (FTIR-Raman)

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The formation of prepared phases has been confirmed by powder FTIR and Raman spectroscopies, the vibrational spectra for different amounts of substitution have been acquired

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and presented on (Fig 9) and measured band positions (Frequencies, cm−1) are listed in Tables3 and 4. All spectra are rather similar, in agreement with the same structural vibrational features observed on Bi-replaced apatite compounds [45-46]. In general, samples show a structural organization at short range. On both Raman and infrared spectra, the bands are due to the vibrations of the phosphate groups. The factor group analysis of HAp has been reported by [26, 47-48]. In terms of symmetry, an isolated phosphate ion (PO4)3-possesses four normal internal vibrational modes: 1A1(ν1) + 1E(ν2) + 2T2 (ν3 and ν4). Where A1 is non degenerate symmetric stretching

mode,

E

and

T2

are

doublysymmetric

bending

mode

and

triply

degenerateantisymmetric stretching and bending modes, respectively. In the ionic crystal, local symmetry is partially preserved by that ν1 (900-1000 cm-1) andν2 (400-450 cm-1) modes are more active in Raman spectra, while ν3 (1000-1200 cm-1) and ν4 (500-650 cm-1) modes are intense in infrared[47,48].For HAp phase, 3n atoms give rise to 132 vibrational modes: 54 internal PO4 modes, 2 internal OH modes, 18 libratory PO4 lattice modes, 4 libratory OH lattice modes, and 54 translatory lattice modes resulting from translations of the 18 ions in the unit cell[48]. 11

Journal Pre-proof The number of bands predicted by group theory calculations in space group P63/m (C26h) is two for ν1, three for ν2 and five for the ν3 and ν4 phosphate group modes. The OH-ions of the HAp add a stretching mode at 3600 cm-1, a libration band at 630 cm-1 and a translational at 340 cm-1 in the Raman spectra [49-50]. In the FTIR spectra, bands at 3426-3442 cm-1are assigned to hydroxyl stretching mode, weak band observed at 1635 cm−1 were associated to absorbed water in the samples and/or in the KBr pellet [51].The weak peaks at 919-950 cm-1and broad bands at 1043-1104 cm-1are assigned to 1 and 3 stretching modes respectively of (PO4)3- group, while correspond to. In the region 600500 cm-1exists intense bands are relative to 4 (PO4)3-, and weak peaks of OH group belongs to

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typical HAp structure, which gradually decrease as Bi content is increased, it is clearly seen that with addition of Bi FTIR spectra show broad bands indicating decrease in the degree of

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crystallization same behavior was observed by other authors [31].On the other side Raman correspond to component 2 of (PO4)3- group.

re

1

-p

spectra show intense peaks at 964 cm-1 assigned to 1 (PO4)3- and medium peaks at 440-456cm-

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Table 2: FT-IR Bands assignments of HAp-Bi phases FTIR Frequencies (cm-1) 3PO43as P-O

3442

1 PO43s P-O

2 (PO4 )3-

O-P-O strong

O-P-O weak

950

637

469

600

424

Ca10(PO4)6(OH)2

635

469

Ca9.85Bi0.1(PO4)6(OH)2

561

421

631

463

Ca9.55Bi0.3(PO4)6(OH)2

426

Ca9.25Bi0.5(PO4)6(OH)2

weak

Jo ur

strong

4 (PO4)3-

na

s O-H

1104 1055

3438

3438

1051

1045

Sample

925

921

565

551 3426

1043

919

623 542

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Journal Pre-proof Table 3: FT-Raman Bands assignments of HAp-Bi phases Raman Frequencies (cm-1) 3PO43as P-O

1 PO43s P-O

Weak 1039

Sample

4 (PO4)3-

2 (PO4 )3-

Strong

O-P-O weak

O-P-O Medium

964

594

456

Ca10(PO4)6(OH)2 964

591

446

Ca9.85Bi0.1(PO4)6(OH)2

1055

964

581

450

Ca9.55Bi0.3(PO4)6(OH)2

1042

963

591

440

of

1051

Jo ur

na

lP

re

-p

ro

Ca9.25Bi0.5(PO4)6(OH)2

13

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HAp-Bi50%

HAp

3000

J

2500

rn

3-

u o PO4)

H2O

2000

l a

1500

Wavenumbers (cm-1)

PO4)

1000

500

o r p

e

HAp-Bi 10%

3500

f o

HAp-Bi30%

Intensity (a.u)

Transmittance (a.u)

HAp:-Bi 30%

OHap

B

HAp-Bi50%

A

r P

HAp-Bi10%

HAp

 (PO4)

3300

400

500

 (PO4)

3600

700

800

900

3-

1000

1100

wavenumbers (cm-1)

Fig. 9. Vibrational spectra of HAp-Bi phases, (A) FTIR, (B) Raman

14

Journal Pre-proof 3.4. Dielectric properties of HAp-Bi ceramics The dielectrical properties of the Bismuth substituted HAp ceramics were measured to determine the dielectrical parameters. The dielectric constant (ε) dependence of frequency of the samples is shown in Fig.10. In general, the values of the dielectric constant are due to the contributions of electronic components, ionic and dipole orientation contributions to polarizability [52-53], and are determined experimentally by the relation (10) [54]. = 𝐶𝑙/0𝐴

(10)

Where C is the capacitance of the sample, 𝑙 is the thickness of the sample,0 is the permittivity of the vacuum, and A is the area of cross-section of the sample pellet. The dielectric properties of

of

HAp are reported in [55], where the variation of dielectric properties versus frequency reveals

ro

the normal dielectric behavior of the material. It is well known that the conduction mechanism in HAp phase is related to the proton movement along the c-axis between O2- anion or to an (OH)-

-p

ion interacting with the double bonded oxygen of PO4 groups [56]. On the other hand, it is believed that OH–ion in HAp structure contributes to the ionic conduction at elevated

re

temperature [57]. However, at room temperature, the HAp conductivity is caused by the

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migration of proton in adsorbed or condensed water [58].

The calculated values of dielectric constant at 1 kHz frequency were found to be 12.56, 10.20,

na

10.03 and 11.32 for HAp, HAp-10%Bi, HAp-30%Bi and HAp-50%Bi, respectively. These values are in good agreement with the reported values given in the literature for the HAp [24, 59–60].

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The dielectric constant values vary with increasing frequency, as well as Bi content(Fig.9),The dielectric constant decreased firstly for HAp-10%Bi and HAp-30%Bi and then slightly increased for HAp-50%Bi. This change in the dielectric constant is due the electrical polarization in the ceramics. The incorporation of Bi into Ca site in HAp changes the dielectric dipole moments of the OH- ions. For HAp-50%Bi the slight increase in dielectric constant maybe caused by the formation of new phase, α-TCP, in the sample [61]. Figs. 11 and 12 show the plots of dielectric loss as a function of frequency at room temperature. The dielectric loss was determined by equation (11).It is observed that dielectric loss is gradually decreases. For all the samples, a relaxation peak was observed at about 4.6MHz. ε″ =tanδ ε

(11)

The alternating electrical conductivity (AC) of the ceramics is shown in Fig. 13. And calculated using the following relation (12) at room temperature the AC conductivity linearly increases with 15

Journal Pre-proof increasing frequency As well, the alternating current conductivity of HAp gradually decreases with the addition of Bi. Same behavior was observed for other HAp ceramics incorporated trivalent cations. [24,41]. σac = l/ZA

0

200000

400000

-p

ro

of



HAp HAp-Bi10% HAp-Bi30% HAp-Bi50%

600000

800000

1000000

re

F(Hz)

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Fig. 10: Plots of ε vs. f of HAp-Bi ceramics

Tg

Jo ur

na

HAp HAp-Bi10% HAp-Bi30% HAp-Bi50%

0

200000

400000

600000

800000

1000000

1200000

F(Hz)

Fig. 11. Dielectric loss as a function of frequency plots of the as-synthesized samples.

16

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Log Tg

HAp HAp-Bi10% HAp-Bi30% HAp-Bi50%

10000

100000

1000000

Log F

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Fig. 12. Log of Dielectric loss as a function of Log frequency plots of the as-synthesized samples.

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HAp HAp-Bi10% HAp-Bi30% HAp-Bi50% 600000

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Fig. 13. Alternating current conductivity vs. frequency plots of the as-prepared samples.

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4. Conclusion Micro crystalline HAp samples substituted by 0, 10, 30 and 50 at% Bi were synthesized by solid state method, and they were characterized by XRD, SEM, FTIR and Raman spectroscopies. Samples were crystallized in hexagonal system with P63/m space group. The formation of the HAp phase in all samples was further proved by vibrational spectra. Lattice parameters and the unit cell volume were slightly affected by Bi content.The crystallite size was investigated by Debye scherrer and William-Hall methods, which both revealed decrease in crystallite size by addition of Bi in HAp lattice. The morphological analysis revealed a random distribution of

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micro sized grains with irregular shapes, while vibrational studies confirmed the existence of 4 vibrational modes of (PO4)3- group ʋ1andʋ2 are observed in Raman spectra whereas ʋ3andʋ4 in

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FTIR spectra.The relative permittivity, dielectric loss and alternating current conductivity change

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with increasing frequency, the alternating conductivity gradually decreases with the addition of

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Bi, while the sample HAp-Bi 50% presents the optimal dielectric properties.

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Acknowledgement

Authors would like to thank center of analysis and characterization (CAC) faculty of sciences

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semalalia Marrakech, for the characterization of our materials. Project partially supported by CNRST (Morocco) -CNR (Italy) bilateral project 2016-2017 ‘Novel Ca9RE(PO4)7biomaterials:

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synthesis and multi-methodological characterization via X-ray techniques.

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Whittles Publishing (2008)

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properties of hydroxyapatite based ceramics, Cardiff University, Cardiff, UK. Published by

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Graphical Abstract

Figure : Solid state synthesis method of HAp-Bi phases

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Highlights - We reported a facile solid state method to synthesize new phases of hydroxyapatite substituted by bismuth element. - Samples were characterized by DRX, SEM, FTIR and Raman.

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- Morphological, dielectrical and vibrational properties were investigated.

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