Lahcen BIH - Academia.edu (original) (raw)
Papers by Lahcen BIH
Crystals
Owing to their low dielectric loss and high permittivity values, dielectric ceramics have garnere... more Owing to their low dielectric loss and high permittivity values, dielectric ceramics have garnered a lot of interest from the scientific and industrial sectors. These properties allow for their downsizing and use in a variety of electronic circuits. This present work focuses on the impact of the substitution of W6+ with Mo6+ on the structural and dielectric features of the crystalline phases in a similar TTB structure within the Ba0.54Na0.46Nb1.29W(0.37−x)MoxO5 system, with 0 ≤ x ≤ 0.33 mol%. These crystalline phases were elaborated using the conventional solid-state reaction method and analyzed with XRD, Raman, and dielectric techniques. The Rietveld refinement method showed that all these phases are characterized by tetragonal structure and the P4bm space group. The Raman spectra corresponded well to a TTB-like structure, and all the bands were assigned. The dielectric measurements of the prepared ceramic samples facilitated the determination of their phase transition temperature ...
Journal of Materials Science: Materials in Electronics, 2022
We report the structural and dielectric properties of new PrFeTiO5 oxide. The crystal structure w... more We report the structural and dielectric properties of new PrFeTiO5 oxide. The crystal structure was refined by X-ray powder diffraction data in the orthorhombic Pbam space group and cell parameters a = 7.6107(2) Å, b = 8.7416(2) Å and c = 5.8497(2). The dielectric properties of the sample were studied in the frequency range of 10 Hz to 1 MHz at several temperatures from 303 to 563 K. The characteristics of a giant dielectric constant were observed in the curves representing the temperature dependence of the dielectric constant with an anomaly occurring at T = 483 K which reduces ε' at high temperature. To determine the possible mechanism that describes the dielectric properties of PrFeTiO5, and to probe the origin of the anomaly observed, the frequency dependence of the real and imaginary parts of the complex permittivity, impedance, modulus, and ac conductivity were investigated. The complex permittivity was analyzed by the modified Cole–Cole equation, it exhibits two relaxation processes, Debye-type dipole relaxation in the high-frequency domain, and charge carrier response associated with long-range migration at low-frequency region. The complex impedance, modulus, and ac conductivity confirm that the microstructure consists of high-conductive grains and low-conductive grain boundaries, as well as the Maxwell–Wagner relaxation process in this compound. The real part of the ac conductivity was used to determine the hopping mechanism occurring in grains and grain boundaries. Two temperature regions have been distinguished: (i) T < 483 K, the conduction mechanisms in grains and grain boundaries have the same activation energy of 0.4 eV, and the observed relaxation process is probably governed by trap-controlled ac conduction. (ii) T > 483 K, grain boundaries are dominant with activation energy of 0.9 eV, this relaxation process is probably due to the movement of oxygen vacancies. The anomaly observed at 483 K is found to be related to the change in the conduction mechanism and the nature of charge carriers in the grain boundaries. The dispersion observed at low frequencies and high temperatures was interpreted in terms of Schottky barriers formation upon the electrodes which block the charge carriers.
Journal of Non-Crystalline Solids, 2014
ABSTRACT The glasses in the Na2O–SrO–BaO–TiO2–B2O3–P2O5 system were prepared by the conventional ... more ABSTRACT The glasses in the Na2O–SrO–BaO–TiO2–B2O3–P2O5 system were prepared by the conventional quenching route. In the present work, we studied the effect of BaSr substitution on some physical parameters such as density, molar volume, micro-hardness, glass transition temperature (Tg), and crystallization temperature (Tc) of series of glasses with the following composition 33.33Na2O–(10 − x)SrO − xBaO–10TiO2–30B2O3–16.67P2O5. The crystallization of the glasses by heat-treatments is performed and X-ray diffraction (XRD) showed the formation of a ferroelectric phase SrTiO3 and Na4Ba2(PO3)6 in their network. The kinetic of the crystallization is carried out by using DSC technique, and the activation energy and the Avrami parameter (n) are determined.
Several studies have been reported on lithium phosphate glasses to which lithium halides and lith... more Several studies have been reported on lithium phosphate glasses to which lithium halides and lithium sulphate have been added However, there has been no experimental results for the introduction of sodium fluoride into the lithium tungsten phosphate network How specifically this feature - mixed alkali in the presence of fluorine ion - influences ion transport in the glasses is unclear. This work concerns the investigation of ion transport behaviour of NaF containing lithium tungsten phosphate glasses in order to understand better the role of NaF in the ionic cation transport Glasses obtained in the system 0.5[x(2NaF)-(1-x)Li2O]-0.5[0.25(WO3)(2)-0.75P(2)O(5)] were investigated The glass samples have been characterised using powder X-ray diffraction (XRD), thermal analysis, density and impedance spectroscopy X-ray diffraction and thermal studies have confirmed that these glasses can be formed in the range x = 0 to 1 The mixed alkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glasses and this has been attributed to a mixed alkali influence on the electrical conduction in these systems.
Journal of Thermal Analysis and Calorimetry, 2012
By means of the conventional quenching route, the glass series 33Na 2 O-xSrO-xTiO 2-(50-2x)B 2 O ... more By means of the conventional quenching route, the glass series 33Na 2 O-xSrO-xTiO 2-(50-2x)B 2 O 3-17P 2 O 5 (x = 0-12.5 mol%) were prepared. The amorphous state of samples was verified by X-ray diffraction (XRD). Density, molar volume, micro-hardness, glass transition temperature (T g), and crystallization temperature (T c) parameters are determined for each glass. The results show that they depend strongly on the chemical compositions. The structure approach of the glasses is determined by Infrared spectroscopy (IR). This investigation highlights that the glassy-matrix contains various phosphate and borate structural units. The crystallization of the high-TiO 2 glasses by heat-treatments favors the formation of titanate phosphate Na 4 TiO(PO 4) 2 or Sr 0.5 Ti 2 (PO 4) 3 along with Sr 3 (PO 4) 2 inside the glass-matrix.
Journal of Molecular Structure, 2011
In the present study we report the synthesis, crystal structure and Raman spectroscopy studies of... more In the present study we report the synthesis, crystal structure and Raman spectroscopy studies of Na 1Àx K x Pb 4 (VO 4) 3 orthovanadates solid solutions (0 6 x 6 1). Rietveld refinements showed that this solid solution is continuous adopting P6 3 /m (no. 176) space group. Some of Pb(II) cations are located in the (6 h) sites. The ninefold coordination sites (4f) are equally occupied by the other lead cations and the K + and Na + monovalent ions. The structure can be described as built up from [VO 4 ] 3À tetrahedral and Pb 2+ of sixfold coordination cavities (6 h positions), which delimit void hexagonal tunnels running along [0 0 1]. These tunnels are connected by cations of mixed sites (4f) half occupied by Pb(II) and half by Na + /K + mixed cations. The existence of this type of lacunar apatite seems to be conditioned by the presence of lone pair cations Pb(II). Raman spectra of all the compositions are similar and show some linear shifts in band positions as a function of the composition toward high values due the substitutions of Na + by K + with a larger radius. No considerable changes in the temperature dependence of the Raman modes and the corresponding FWHM are observed and thus no temperature induced phase transition is observed in Na 0.5 K 0.5 Pb 4 (VO 4) 3 up to 650 K.
Journal of Molecular Structure, 2011
X-ray structure refinement of solid solution Ba 2.15Àx Na 0.7+x Nb 5Àx W x O 15 and the investiga... more X-ray structure refinement of solid solution Ba 2.15Àx Na 0.7+x Nb 5Àx W x O 15 and the investigation of the orthorhombic-tetragonal phase transition by Raman spectroscopy
Журнал структурной химии, 2020
Sr1.50Ca1.50Fe2.25Mo0.75O9–δ and Sr1.92Ca1.08Fe2.04W0.96O9–δ double perovskites are synthesized i... more Sr1.50Ca1.50Fe2.25Mo0.75O9–δ and Sr1.92Ca1.08Fe2.04W0.96O9–δ double perovskites are synthesized in the polycrystalline form by a solid-state reaction route in air and studied at room temperature using the of PXRD, Raman and Mössbauer spectroscopy techniques. The Rietveld refinement analysis reveals that both compounds adopt a tetragonal system with the space group I4/m and lattice parameters a = b = 5.5176(1) Å and c = 7.8065(2) Å for Sr1.50Ca1.50Fe2.25Mo0.75O9–δ and a = b = 5.5453(1) Å and c = 7.8388(1) Å for Sr1.92Ca1.08Fe2.04W0.96O9–δ. Raman spectra are consistent with the group theoretical analysis predicted for tetragonal symmetry I4/m (point group C4h5). 57Fe Mössbauer spectra recorded at room temperature show a paramagnetic behavior for Sr1.50Ca1.50Fe2.25Mo0.75O9–δ, and magnetic ordering for Sr1.92Ca1.08Fe2.04W0.96O9–δ. The isomer shift (δ) and quadrupole splitting (Δ) values are characteristic of high-spin Fe3+ in a distorted octahedral coordination.
Materials Today: Proceedings
20K 2 O-30TiO 2-50P 2 O 5 (KTP) glass was elaborated by conventional quenching method. The densit... more 20K 2 O-30TiO 2-50P 2 O 5 (KTP) glass was elaborated by conventional quenching method. The density and molar volume values of KTP glass are determined. The structure of the glass was performed by Raman spectroscopy. The results revealed that KTP glass consists mainly of orthophosphate and pyrophosphate units, and the titanium occupies the octahedral sites in the glassy matrix. The controlled crystallization of KTP glass was carried out to develop glass-ceramic (GC-KTP). X-ray diffraction was used to identify the crystallized phases in (GC-KTP). Dielectric and conductivity parameters of the glass-ceramic are determined by impedance spectroscopy in the frequency range of 300 Hz to 1 MHz under various temperatures from 300 to 473 K. The results obtained showed that the dielectric parameters (permittivity and dielectric losses) increase at high-temperature and low-frequency and the conductivity is thermally activated and follows the Arrhenius behavior.
Glasses in the system 33.33[xNa2O-(1-x)Li2O]-2.5SrO-2.5TiO2-45B2O3-16.67P2O5 (0.0 ≤ x ≤ 1.0) were... more Glasses in the system 33.33[xNa2O-(1-x)Li2O]-2.5SrO-2.5TiO2-45B2O3-16.67P2O5 (0.0 ≤ x ≤ 1.0) were prepared by standard melt quenching procedures, and their physical properties were characterized by thermal analysis, density measurements. Their local structures were comprehensively characterized by Infrared spectroscopy (IR) and electron paramagnetic resonance (EPR). The variation of the glass transition temperature as a function of the glass compositions is non-linear. The infrared spectroscopy of the glasses has identified the presence of different structural grouping units in the glassy-matrix. It is found that the stretching and bending vibration modes of borate groups are more sensitive to the substitution of alkali elements. EPR experiments have shown the presence of Ti3+ centres in the glasses. The variation of the g-factor as a function of the Na/(Na+Li) ratio presents a minimum around (x=0.5). The composition non-linearity behavior of Tg, vibration bending mode, and g-factor...
Dielectric Materials and Applications - ISyDMA’2016, 2016
Phosphate glasses of the compositions 20Li(2)O-(50-x)Li2WO4-xTiO(2)-30P(2)O(3) (0 <= x <= 1... more Phosphate glasses of the compositions 20Li(2)O-(50-x)Li2WO4-xTiO(2)-30P(2)O(3) (0 <= x <= 15, mol%) were prepared by the melt quenching method. The amorphous nature of these glasses was confi ...
Ceramics International, 2020
Design and characterization of novel manganite perovskites Ba 1-x Bi x Ti 1-x Mn x O 3 (0≤x≤0.2),
Materials Today: Proceedings, 2020
Silver phosphate glasses in the Ag 2 O-Nb 2 O 5-P 2 O 5 ternary system were prepared using the co... more Silver phosphate glasses in the Ag 2 O-Nb 2 O 5-P 2 O 5 ternary system were prepared using the conventional quenching method. The glasses were defined by the 50Ag 2 O-xNb 2 O 5-(50-x)P 2 O 5 composition with 0 x 25 mol %. They were found coloured. Their density and molar volume values are examined. The X-ray diffraction analysis was confirmed their amorphous state. The glass-ceramics were achieved by performing heat treatments of the elaborated glasses. To highlighting the impact of replacing P 2 O 5 by Nb 2 O 5 on the structural properties of the elaborated glasses and glass-ceramics, Raman analysis was carried out. This technique permitted the identification of various structural units of phosphate, mainly metaphosphates and pyrophosphate, and revealed that niobium adopts an octahedral oxygen environment. The controlled crystallization of the glasses leads to the formation of an orthorhombic silver niobate phase AgNbO 3 mixed with a secondary phase Ag 4 P 2 O 7 for glasses with high niobium content (x ! 15 mol%) and AgPO 3 for glasses with low niobium concentration (x 15 mol%).
Journal of Thermal Analysis and Calorimetry, 2020
Glasses in the system (1 − x)(0.5NaPO 3-0.5KPO 3)-xMnO 2 , with 0 ≤ x ≤ 50 mol%, have been prepar... more Glasses in the system (1 − x)(0.5NaPO 3-0.5KPO 3)-xMnO 2 , with 0 ≤ x ≤ 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn 2+ and Mn 3+ ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (T g) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (ρ) as a structural index is found to increase while the corresponding molar volume decreases with MnO 2 content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn 2+ centers in the glasses. The UV-Visible absorption is utilized to estimate the values of the optical band gap (E g) and Urbach energy (ΔE). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc's methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (E c) and the Avrami parameter (n) were determined.
Materials Research Express, 2019
Ferroelectric glass-ceramics are promising composite materials with dual properties, of high diel... more Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na 2 O-2.5[(1-x)Nb 2 O 5-xWO 3 ]-1P 2 O 5 (x=0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), X-ray powder diffraction (XRD), Raman, impedance spectroscopy, and the P-E hysteresis loops. All of these techniques allowed the identification of Ba 2 Na 4 W 2 Nb 8 O 30 phase with tungsten bronze structure embedded in the glassy matrix. The density of glass-ceramics was found to increase with increasing tungsten content to reach a maximum at x =0.3 and then decreases. Dielectric and conductivity parameters were found to be governed by the presence of oxygen vacancies. Room temperature energy storage property which depends on the composition X, was performed using P-E hysteresis loops of the glass-ceramics. The optimum discharge density was obtained for B3 with an energy efficiency of 73.77%.
Crystals
Owing to their low dielectric loss and high permittivity values, dielectric ceramics have garnere... more Owing to their low dielectric loss and high permittivity values, dielectric ceramics have garnered a lot of interest from the scientific and industrial sectors. These properties allow for their downsizing and use in a variety of electronic circuits. This present work focuses on the impact of the substitution of W6+ with Mo6+ on the structural and dielectric features of the crystalline phases in a similar TTB structure within the Ba0.54Na0.46Nb1.29W(0.37−x)MoxO5 system, with 0 ≤ x ≤ 0.33 mol%. These crystalline phases were elaborated using the conventional solid-state reaction method and analyzed with XRD, Raman, and dielectric techniques. The Rietveld refinement method showed that all these phases are characterized by tetragonal structure and the P4bm space group. The Raman spectra corresponded well to a TTB-like structure, and all the bands were assigned. The dielectric measurements of the prepared ceramic samples facilitated the determination of their phase transition temperature ...
Journal of Materials Science: Materials in Electronics, 2022
We report the structural and dielectric properties of new PrFeTiO5 oxide. The crystal structure w... more We report the structural and dielectric properties of new PrFeTiO5 oxide. The crystal structure was refined by X-ray powder diffraction data in the orthorhombic Pbam space group and cell parameters a = 7.6107(2) Å, b = 8.7416(2) Å and c = 5.8497(2). The dielectric properties of the sample were studied in the frequency range of 10 Hz to 1 MHz at several temperatures from 303 to 563 K. The characteristics of a giant dielectric constant were observed in the curves representing the temperature dependence of the dielectric constant with an anomaly occurring at T = 483 K which reduces ε' at high temperature. To determine the possible mechanism that describes the dielectric properties of PrFeTiO5, and to probe the origin of the anomaly observed, the frequency dependence of the real and imaginary parts of the complex permittivity, impedance, modulus, and ac conductivity were investigated. The complex permittivity was analyzed by the modified Cole–Cole equation, it exhibits two relaxation processes, Debye-type dipole relaxation in the high-frequency domain, and charge carrier response associated with long-range migration at low-frequency region. The complex impedance, modulus, and ac conductivity confirm that the microstructure consists of high-conductive grains and low-conductive grain boundaries, as well as the Maxwell–Wagner relaxation process in this compound. The real part of the ac conductivity was used to determine the hopping mechanism occurring in grains and grain boundaries. Two temperature regions have been distinguished: (i) T < 483 K, the conduction mechanisms in grains and grain boundaries have the same activation energy of 0.4 eV, and the observed relaxation process is probably governed by trap-controlled ac conduction. (ii) T > 483 K, grain boundaries are dominant with activation energy of 0.9 eV, this relaxation process is probably due to the movement of oxygen vacancies. The anomaly observed at 483 K is found to be related to the change in the conduction mechanism and the nature of charge carriers in the grain boundaries. The dispersion observed at low frequencies and high temperatures was interpreted in terms of Schottky barriers formation upon the electrodes which block the charge carriers.
Journal of Non-Crystalline Solids, 2014
ABSTRACT The glasses in the Na2O–SrO–BaO–TiO2–B2O3–P2O5 system were prepared by the conventional ... more ABSTRACT The glasses in the Na2O–SrO–BaO–TiO2–B2O3–P2O5 system were prepared by the conventional quenching route. In the present work, we studied the effect of BaSr substitution on some physical parameters such as density, molar volume, micro-hardness, glass transition temperature (Tg), and crystallization temperature (Tc) of series of glasses with the following composition 33.33Na2O–(10 − x)SrO − xBaO–10TiO2–30B2O3–16.67P2O5. The crystallization of the glasses by heat-treatments is performed and X-ray diffraction (XRD) showed the formation of a ferroelectric phase SrTiO3 and Na4Ba2(PO3)6 in their network. The kinetic of the crystallization is carried out by using DSC technique, and the activation energy and the Avrami parameter (n) are determined.
Several studies have been reported on lithium phosphate glasses to which lithium halides and lith... more Several studies have been reported on lithium phosphate glasses to which lithium halides and lithium sulphate have been added However, there has been no experimental results for the introduction of sodium fluoride into the lithium tungsten phosphate network How specifically this feature - mixed alkali in the presence of fluorine ion - influences ion transport in the glasses is unclear. This work concerns the investigation of ion transport behaviour of NaF containing lithium tungsten phosphate glasses in order to understand better the role of NaF in the ionic cation transport Glasses obtained in the system 0.5[x(2NaF)-(1-x)Li2O]-0.5[0.25(WO3)(2)-0.75P(2)O(5)] were investigated The glass samples have been characterised using powder X-ray diffraction (XRD), thermal analysis, density and impedance spectroscopy X-ray diffraction and thermal studies have confirmed that these glasses can be formed in the range x = 0 to 1 The mixed alkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glasses and this has been attributed to a mixed alkali influence on the electrical conduction in these systems.
Journal of Thermal Analysis and Calorimetry, 2012
By means of the conventional quenching route, the glass series 33Na 2 O-xSrO-xTiO 2-(50-2x)B 2 O ... more By means of the conventional quenching route, the glass series 33Na 2 O-xSrO-xTiO 2-(50-2x)B 2 O 3-17P 2 O 5 (x = 0-12.5 mol%) were prepared. The amorphous state of samples was verified by X-ray diffraction (XRD). Density, molar volume, micro-hardness, glass transition temperature (T g), and crystallization temperature (T c) parameters are determined for each glass. The results show that they depend strongly on the chemical compositions. The structure approach of the glasses is determined by Infrared spectroscopy (IR). This investigation highlights that the glassy-matrix contains various phosphate and borate structural units. The crystallization of the high-TiO 2 glasses by heat-treatments favors the formation of titanate phosphate Na 4 TiO(PO 4) 2 or Sr 0.5 Ti 2 (PO 4) 3 along with Sr 3 (PO 4) 2 inside the glass-matrix.
Journal of Molecular Structure, 2011
In the present study we report the synthesis, crystal structure and Raman spectroscopy studies of... more In the present study we report the synthesis, crystal structure and Raman spectroscopy studies of Na 1Àx K x Pb 4 (VO 4) 3 orthovanadates solid solutions (0 6 x 6 1). Rietveld refinements showed that this solid solution is continuous adopting P6 3 /m (no. 176) space group. Some of Pb(II) cations are located in the (6 h) sites. The ninefold coordination sites (4f) are equally occupied by the other lead cations and the K + and Na + monovalent ions. The structure can be described as built up from [VO 4 ] 3À tetrahedral and Pb 2+ of sixfold coordination cavities (6 h positions), which delimit void hexagonal tunnels running along [0 0 1]. These tunnels are connected by cations of mixed sites (4f) half occupied by Pb(II) and half by Na + /K + mixed cations. The existence of this type of lacunar apatite seems to be conditioned by the presence of lone pair cations Pb(II). Raman spectra of all the compositions are similar and show some linear shifts in band positions as a function of the composition toward high values due the substitutions of Na + by K + with a larger radius. No considerable changes in the temperature dependence of the Raman modes and the corresponding FWHM are observed and thus no temperature induced phase transition is observed in Na 0.5 K 0.5 Pb 4 (VO 4) 3 up to 650 K.
Journal of Molecular Structure, 2011
X-ray structure refinement of solid solution Ba 2.15Àx Na 0.7+x Nb 5Àx W x O 15 and the investiga... more X-ray structure refinement of solid solution Ba 2.15Àx Na 0.7+x Nb 5Àx W x O 15 and the investigation of the orthorhombic-tetragonal phase transition by Raman spectroscopy
Журнал структурной химии, 2020
Sr1.50Ca1.50Fe2.25Mo0.75O9–δ and Sr1.92Ca1.08Fe2.04W0.96O9–δ double perovskites are synthesized i... more Sr1.50Ca1.50Fe2.25Mo0.75O9–δ and Sr1.92Ca1.08Fe2.04W0.96O9–δ double perovskites are synthesized in the polycrystalline form by a solid-state reaction route in air and studied at room temperature using the of PXRD, Raman and Mössbauer spectroscopy techniques. The Rietveld refinement analysis reveals that both compounds adopt a tetragonal system with the space group I4/m and lattice parameters a = b = 5.5176(1) Å and c = 7.8065(2) Å for Sr1.50Ca1.50Fe2.25Mo0.75O9–δ and a = b = 5.5453(1) Å and c = 7.8388(1) Å for Sr1.92Ca1.08Fe2.04W0.96O9–δ. Raman spectra are consistent with the group theoretical analysis predicted for tetragonal symmetry I4/m (point group C4h5). 57Fe Mössbauer spectra recorded at room temperature show a paramagnetic behavior for Sr1.50Ca1.50Fe2.25Mo0.75O9–δ, and magnetic ordering for Sr1.92Ca1.08Fe2.04W0.96O9–δ. The isomer shift (δ) and quadrupole splitting (Δ) values are characteristic of high-spin Fe3+ in a distorted octahedral coordination.
Materials Today: Proceedings
20K 2 O-30TiO 2-50P 2 O 5 (KTP) glass was elaborated by conventional quenching method. The densit... more 20K 2 O-30TiO 2-50P 2 O 5 (KTP) glass was elaborated by conventional quenching method. The density and molar volume values of KTP glass are determined. The structure of the glass was performed by Raman spectroscopy. The results revealed that KTP glass consists mainly of orthophosphate and pyrophosphate units, and the titanium occupies the octahedral sites in the glassy matrix. The controlled crystallization of KTP glass was carried out to develop glass-ceramic (GC-KTP). X-ray diffraction was used to identify the crystallized phases in (GC-KTP). Dielectric and conductivity parameters of the glass-ceramic are determined by impedance spectroscopy in the frequency range of 300 Hz to 1 MHz under various temperatures from 300 to 473 K. The results obtained showed that the dielectric parameters (permittivity and dielectric losses) increase at high-temperature and low-frequency and the conductivity is thermally activated and follows the Arrhenius behavior.
Glasses in the system 33.33[xNa2O-(1-x)Li2O]-2.5SrO-2.5TiO2-45B2O3-16.67P2O5 (0.0 ≤ x ≤ 1.0) were... more Glasses in the system 33.33[xNa2O-(1-x)Li2O]-2.5SrO-2.5TiO2-45B2O3-16.67P2O5 (0.0 ≤ x ≤ 1.0) were prepared by standard melt quenching procedures, and their physical properties were characterized by thermal analysis, density measurements. Their local structures were comprehensively characterized by Infrared spectroscopy (IR) and electron paramagnetic resonance (EPR). The variation of the glass transition temperature as a function of the glass compositions is non-linear. The infrared spectroscopy of the glasses has identified the presence of different structural grouping units in the glassy-matrix. It is found that the stretching and bending vibration modes of borate groups are more sensitive to the substitution of alkali elements. EPR experiments have shown the presence of Ti3+ centres in the glasses. The variation of the g-factor as a function of the Na/(Na+Li) ratio presents a minimum around (x=0.5). The composition non-linearity behavior of Tg, vibration bending mode, and g-factor...
Dielectric Materials and Applications - ISyDMA’2016, 2016
Phosphate glasses of the compositions 20Li(2)O-(50-x)Li2WO4-xTiO(2)-30P(2)O(3) (0 <= x <= 1... more Phosphate glasses of the compositions 20Li(2)O-(50-x)Li2WO4-xTiO(2)-30P(2)O(3) (0 <= x <= 15, mol%) were prepared by the melt quenching method. The amorphous nature of these glasses was confi ...
Ceramics International, 2020
Design and characterization of novel manganite perovskites Ba 1-x Bi x Ti 1-x Mn x O 3 (0≤x≤0.2),
Materials Today: Proceedings, 2020
Silver phosphate glasses in the Ag 2 O-Nb 2 O 5-P 2 O 5 ternary system were prepared using the co... more Silver phosphate glasses in the Ag 2 O-Nb 2 O 5-P 2 O 5 ternary system were prepared using the conventional quenching method. The glasses were defined by the 50Ag 2 O-xNb 2 O 5-(50-x)P 2 O 5 composition with 0 x 25 mol %. They were found coloured. Their density and molar volume values are examined. The X-ray diffraction analysis was confirmed their amorphous state. The glass-ceramics were achieved by performing heat treatments of the elaborated glasses. To highlighting the impact of replacing P 2 O 5 by Nb 2 O 5 on the structural properties of the elaborated glasses and glass-ceramics, Raman analysis was carried out. This technique permitted the identification of various structural units of phosphate, mainly metaphosphates and pyrophosphate, and revealed that niobium adopts an octahedral oxygen environment. The controlled crystallization of the glasses leads to the formation of an orthorhombic silver niobate phase AgNbO 3 mixed with a secondary phase Ag 4 P 2 O 7 for glasses with high niobium content (x ! 15 mol%) and AgPO 3 for glasses with low niobium concentration (x 15 mol%).
Journal of Thermal Analysis and Calorimetry, 2020
Glasses in the system (1 − x)(0.5NaPO 3-0.5KPO 3)-xMnO 2 , with 0 ≤ x ≤ 50 mol%, have been prepar... more Glasses in the system (1 − x)(0.5NaPO 3-0.5KPO 3)-xMnO 2 , with 0 ≤ x ≤ 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn 2+ and Mn 3+ ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (T g) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (ρ) as a structural index is found to increase while the corresponding molar volume decreases with MnO 2 content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn 2+ centers in the glasses. The UV-Visible absorption is utilized to estimate the values of the optical band gap (E g) and Urbach energy (ΔE). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc's methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (E c) and the Avrami parameter (n) were determined.
Materials Research Express, 2019
Ferroelectric glass-ceramics are promising composite materials with dual properties, of high diel... more Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na 2 O-2.5[(1-x)Nb 2 O 5-xWO 3 ]-1P 2 O 5 (x=0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), X-ray powder diffraction (XRD), Raman, impedance spectroscopy, and the P-E hysteresis loops. All of these techniques allowed the identification of Ba 2 Na 4 W 2 Nb 8 O 30 phase with tungsten bronze structure embedded in the glassy matrix. The density of glass-ceramics was found to increase with increasing tungsten content to reach a maximum at x =0.3 and then decreases. Dielectric and conductivity parameters were found to be governed by the presence of oxygen vacancies. Room temperature energy storage property which depends on the composition X, was performed using P-E hysteresis loops of the glass-ceramics. The optimum discharge density was obtained for B3 with an energy efficiency of 73.77%.