marwa jebli - Academia.edu (original) (raw)
Papers by marwa jebli
Journal of Alloys and Compounds, May 1, 2019
Single crystalline homoepitaxial Nb doped TiO 2 (TiO 2 :Nb) films were deposited on rutile TiO 2 ... more Single crystalline homoepitaxial Nb doped TiO 2 (TiO 2 :Nb) films were deposited on rutile TiO 2 (r-TiO 2) (001) substrates by metal organic chemical vapor deposition (MOCVD). Effect of Nb doping on structural and electrical properties of the films were studied. The maximum Hall mobility of the obtained films reached as high as 14.0 cm 2 V −1 s −1 and the lowest resistivity of the films was 1.9 × 10 −1 Ω cm which was 7 orders of magnitude lower than that of pristine r-TiO 2. The obtained films were single crystalline r-TiO 2 epitaxially grown along the (001) orientation. The relationship between the structural and electrical properties was discussed. TiO 2 :Nb films with high mobilities may have many potential applications in the field of transparent electronic devices.
Journal of Molecular Structure, Apr 1, 2022
Journal of Inorganic and Organometallic Polymers and Materials, May 24, 2022
Journal of Inorganic and Organometallic Polymers and Materials, Jan 8, 2022
Ba0.97La0.02Ti0.95Nb0.04O3 polycrystalline sample was produced through molten-salt technique. The... more Ba0.97La0.02Ti0.95Nb0.04O3 polycrystalline sample was produced through molten-salt technique. The morphological, structural, impedance and optical properties were investigated by scanning electron microscope, X-ray powder diffraction (XRD), and ultraviolet–visible diffuse reflectance spectrophotometer, respectively. XRD pattern illustrate a single-pure phase of tetragonal perovskite structure with P4/mmm group space. No impurity was noticed for present ceramic. The optical band gap (Eg) values were calculated from the absorption spectra. Notwithstanding, electrical and dielectric properties were used to analyze the dielectric constant and loss, the modulus as well as dissipation factors as functions of both frequencies and d.c bias voltage for obtained sample. The frequency (f) dependence dielectric study shows that the value of dielectric constant is high at lower frequencies and decreases with increase in frequency. It is obvious to comprehend how to overwhelm the formation of inter-grain and intra-grain, and how to restrain the propagation of Ti species is an important challenge for the realization of an alternative “high-k gate dielectric” applications. Thus, some kind of semicircular arc caused by a variety of electrically active regions can originate from grains, grain boundaries, and electrode polarization effects. The modulus mechanism indicates the non-Debye type of conduction relaxation in the material, which is supported by impedance data.
Journal of Molecular Structure, Feb 1, 2022
Applied Physics A, Jan 18, 2020
Lead-free Ba 0.97 La 0.02 Ti 1−x Nb 4x/5 O 3 (abbreviated as BLT and BLT 0.98 Nb 0.016) ceramics ... more Lead-free Ba 0.97 La 0.02 Ti 1−x Nb 4x/5 O 3 (abbreviated as BLT and BLT 0.98 Nb 0.016) ceramics were grown using the molten-salt method with filtration as well as evaporation technique. A correlation investigation between the morphological, structural, and electrical properties of the system was carried out using impedance spectroscopy at various frequencies (40-10 6 Hz) and temperatures (500-600 K). In the present work, average grain size estimated from the microstructure was ~ 2700 nm. Phase composition was established by the Rietveld refinement, which confirms that our compounds have a single phased nature and crystal structure. They have a tetragonal Perovskite structure with a P4/mmm space group, without any secondary phases. Z′ and Z″ values of impedance decreased with increasing Nb concentration. The EIS data displayed an approximately perfect semicircle at high temperature in the complex plane plot as well as a practically ideal non-Debye peak shape in the spectroscopic plot. The electrical conductivity decreased with increasing niobium amount. The frequency dependence of conductivity plot has been found to obey the universal Jonscher power law. The correlated barrier hoping was established to be the most suitable theoretical model to elucidate the conduction process. These results could help improve the electrical properties of Ba 0.97 La 0.02 Ti 1−x Nb 4x/5 O 3 compounds and understand the relationship between the structure and the electrical properties.
Journal of Materials Science: Materials in Electronics, Jun 1, 2023
Journal of Molecular Structure, Jul 1, 2022
Journal of Materials Science: Materials in Electronics, Jul 16, 2022
Journal of Materials Science: Materials in Electronics, Sep 30, 2021
The chemical molten-salt process was used for the elaboration of a new polycrystalline perovskite... more The chemical molten-salt process was used for the elaboration of a new polycrystalline perovskite compound of Ba0.97La0.02Ti0.95Nb0.04O3 (shortened in BLT0.95Nb0.04). Analysis of XRD patterns using Rietveld refinement reveals that the prepared sample crystallizes in single phase form, with a tetragonal structure, with a P4/mmm space group. Then, a simultaneous investigation of impedance and modulus was effectuated. Complex impedance plots confirm the existence of semicircular arcs which expressed by an electrical equivalent circuit to clarify the impedance consequences. Off-centered semicircular impedance plots makes obvious that the synthesis sample conforms to a non-Debye relaxation manner. Furthermore, it is typically controlled by thermally activated charge carriers. The reducing of resistance, with rising temperature (T), indicates a negative temperature coefficient of resistance, which highlighting that the relaxation process is dominated by the inter-grains.
Journal of Materials Science: Materials in Electronics, Nov 3, 2020
The dielectric properties of polycrystalline ceramic Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 (BLTi 0... more The dielectric properties of polycrystalline ceramic Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 (BLTi 0.98 Nb 0.016), elaborated by a molten-salt reaction, were methodically characterized. Phase purity, structure and crystallinity were examined with X-ray diffraction at room temperature, demonstrating pure phase with tetragonal symmetries and a P4/mmm space group for our sample. The frequency and temperature dependence of the dielectric properties showed an excellent response. The real part of permittivity and dielectric tangent decreased with increasing frequency. This can be clarified by Maxwell-Wagner type of polarization as per with Koop's theory. The temperature dependence of the dielectric properties was examined in the frequency range 1 kHz to 1 MHz. Mostly, these three regions of dielectric relaxations are begun from phase transitions beginning: a cubic-paraelectric to a tetragonal-ferroelectric ''C'' (at the Curie temperature T c), after that to an orthorhombic-ferroelectric ''T ? O'' (at T T ? O), and lastly to a rhombohedral-ferroelectric ''O ? R'' (at T O ? R) resembling to those of pure Barium titanate (BaTiO 3 , BT). To clarify the dielectric phenomenon, the Curie-Weiss law is investigated. This method is used to describe the ferroparaelectric transition. The degree of disorder of the Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 was assessing via the modified Curie-Weiss law. The Raman spectrum was measured at room-temperature, and their variation related to the chemical composition, which affirmed the tetragonal structure for Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 .
Journal of Inorganic and Organometallic Polymers and Materials, Jan 17, 2022
Barium zirconate titanate Ba(Zr y Ti 1Ày)O 3 (BZT, y = 0.2, 0.25, 0.30, 0.35) ceramics have been ... more Barium zirconate titanate Ba(Zr y Ti 1Ày)O 3 (BZT, y = 0.2, 0.25, 0.30, 0.35) ceramics have been prepared by a sol-gel process. The temperature dependence of dielectric permittivity of the ceramics has been investigated. The results show that the phase transition temperature T C (or T m) is suppressed with increasing Zr content. The degree of diffuseness of the phase transition is more pronounced for higher Zr content, implying the existence of a composition-induced diffuse phase transition of the ceramics with 0.20 6 y 6 0.35. For BZT ceramics with y > 0.25, a relaxor ferroelectric characteristic is observed. High tunability and figure of merit are obtained in BZT compositions investigated, which imply that these ceramics are promising materials for tunable capacitor applications.
Inorganic Chemistry Communications, Jul 1, 2021
Abstract In this work, we considered the notable effect of the substitution of Ti4+ by Nb5+ on th... more Abstract In this work, we considered the notable effect of the substitution of Ti4+ by Nb5+ on the structural, electric and dielectric properties of the Ba0.97La0.02Ti1−xNb4x/5O2 (BLTi1−xNb4x/5) compounds for x = 0.02, and 0.07. Our samples were synthesized via the molten-salt method. X-ray diffraction patterns revealed that both compounds have a tetragonal layered perovskite structure with P4/mmm space group. Electrical examination was cruelly focused by complex impedance spectroscopy in the frequency range (10 - 106 Hz). As the concentration of Nb increases, the real (') and imaginary ('') parts of the complex impedance have significantly decreased. The plot typically characterized by a single impedance semicircle for the two compounds, identified over the high and the medium frequencies. As well, at low frequency, followed by a linear section; was represented by the element Warburg. The conductivity decreased with the increase in the amount of niobium. The experimental data were fitted using Jonscher’s universal power law. The dielectric constant (er) has been changed appreciably from 0.5182x103 to 7.7905x103 with the increase in the amount of Nb. The impedance spectroscopic study revealed the presence of a semiconductor grain and an insulating grain boundary. These tow parameters support the internal barrier layer mechanism and are responsible for the high dielectric constant of these materials.
Journal of Inorganic and Organometallic Polymers and Materials, May 29, 2023
Engineering Analysis With Boundary Elements, Mar 1, 2023
Journal of Molecular Structure, Sep 1, 2022
Journal of Molecular Structure, Sep 1, 2022
Applied Physics A, Apr 25, 2022
Journal of Inorganic and Organometallic Polymers and Materials
Journal of Inorganic and Organometallic Polymers and Materials
Journal of Alloys and Compounds, May 1, 2019
Single crystalline homoepitaxial Nb doped TiO 2 (TiO 2 :Nb) films were deposited on rutile TiO 2 ... more Single crystalline homoepitaxial Nb doped TiO 2 (TiO 2 :Nb) films were deposited on rutile TiO 2 (r-TiO 2) (001) substrates by metal organic chemical vapor deposition (MOCVD). Effect of Nb doping on structural and electrical properties of the films were studied. The maximum Hall mobility of the obtained films reached as high as 14.0 cm 2 V −1 s −1 and the lowest resistivity of the films was 1.9 × 10 −1 Ω cm which was 7 orders of magnitude lower than that of pristine r-TiO 2. The obtained films were single crystalline r-TiO 2 epitaxially grown along the (001) orientation. The relationship between the structural and electrical properties was discussed. TiO 2 :Nb films with high mobilities may have many potential applications in the field of transparent electronic devices.
Journal of Molecular Structure, Apr 1, 2022
Journal of Inorganic and Organometallic Polymers and Materials, May 24, 2022
Journal of Inorganic and Organometallic Polymers and Materials, Jan 8, 2022
Ba0.97La0.02Ti0.95Nb0.04O3 polycrystalline sample was produced through molten-salt technique. The... more Ba0.97La0.02Ti0.95Nb0.04O3 polycrystalline sample was produced through molten-salt technique. The morphological, structural, impedance and optical properties were investigated by scanning electron microscope, X-ray powder diffraction (XRD), and ultraviolet–visible diffuse reflectance spectrophotometer, respectively. XRD pattern illustrate a single-pure phase of tetragonal perovskite structure with P4/mmm group space. No impurity was noticed for present ceramic. The optical band gap (Eg) values were calculated from the absorption spectra. Notwithstanding, electrical and dielectric properties were used to analyze the dielectric constant and loss, the modulus as well as dissipation factors as functions of both frequencies and d.c bias voltage for obtained sample. The frequency (f) dependence dielectric study shows that the value of dielectric constant is high at lower frequencies and decreases with increase in frequency. It is obvious to comprehend how to overwhelm the formation of inter-grain and intra-grain, and how to restrain the propagation of Ti species is an important challenge for the realization of an alternative “high-k gate dielectric” applications. Thus, some kind of semicircular arc caused by a variety of electrically active regions can originate from grains, grain boundaries, and electrode polarization effects. The modulus mechanism indicates the non-Debye type of conduction relaxation in the material, which is supported by impedance data.
Journal of Molecular Structure, Feb 1, 2022
Applied Physics A, Jan 18, 2020
Lead-free Ba 0.97 La 0.02 Ti 1−x Nb 4x/5 O 3 (abbreviated as BLT and BLT 0.98 Nb 0.016) ceramics ... more Lead-free Ba 0.97 La 0.02 Ti 1−x Nb 4x/5 O 3 (abbreviated as BLT and BLT 0.98 Nb 0.016) ceramics were grown using the molten-salt method with filtration as well as evaporation technique. A correlation investigation between the morphological, structural, and electrical properties of the system was carried out using impedance spectroscopy at various frequencies (40-10 6 Hz) and temperatures (500-600 K). In the present work, average grain size estimated from the microstructure was ~ 2700 nm. Phase composition was established by the Rietveld refinement, which confirms that our compounds have a single phased nature and crystal structure. They have a tetragonal Perovskite structure with a P4/mmm space group, without any secondary phases. Z′ and Z″ values of impedance decreased with increasing Nb concentration. The EIS data displayed an approximately perfect semicircle at high temperature in the complex plane plot as well as a practically ideal non-Debye peak shape in the spectroscopic plot. The electrical conductivity decreased with increasing niobium amount. The frequency dependence of conductivity plot has been found to obey the universal Jonscher power law. The correlated barrier hoping was established to be the most suitable theoretical model to elucidate the conduction process. These results could help improve the electrical properties of Ba 0.97 La 0.02 Ti 1−x Nb 4x/5 O 3 compounds and understand the relationship between the structure and the electrical properties.
Journal of Materials Science: Materials in Electronics, Jun 1, 2023
Journal of Molecular Structure, Jul 1, 2022
Journal of Materials Science: Materials in Electronics, Jul 16, 2022
Journal of Materials Science: Materials in Electronics, Sep 30, 2021
The chemical molten-salt process was used for the elaboration of a new polycrystalline perovskite... more The chemical molten-salt process was used for the elaboration of a new polycrystalline perovskite compound of Ba0.97La0.02Ti0.95Nb0.04O3 (shortened in BLT0.95Nb0.04). Analysis of XRD patterns using Rietveld refinement reveals that the prepared sample crystallizes in single phase form, with a tetragonal structure, with a P4/mmm space group. Then, a simultaneous investigation of impedance and modulus was effectuated. Complex impedance plots confirm the existence of semicircular arcs which expressed by an electrical equivalent circuit to clarify the impedance consequences. Off-centered semicircular impedance plots makes obvious that the synthesis sample conforms to a non-Debye relaxation manner. Furthermore, it is typically controlled by thermally activated charge carriers. The reducing of resistance, with rising temperature (T), indicates a negative temperature coefficient of resistance, which highlighting that the relaxation process is dominated by the inter-grains.
Journal of Materials Science: Materials in Electronics, Nov 3, 2020
The dielectric properties of polycrystalline ceramic Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 (BLTi 0... more The dielectric properties of polycrystalline ceramic Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 (BLTi 0.98 Nb 0.016), elaborated by a molten-salt reaction, were methodically characterized. Phase purity, structure and crystallinity were examined with X-ray diffraction at room temperature, demonstrating pure phase with tetragonal symmetries and a P4/mmm space group for our sample. The frequency and temperature dependence of the dielectric properties showed an excellent response. The real part of permittivity and dielectric tangent decreased with increasing frequency. This can be clarified by Maxwell-Wagner type of polarization as per with Koop's theory. The temperature dependence of the dielectric properties was examined in the frequency range 1 kHz to 1 MHz. Mostly, these three regions of dielectric relaxations are begun from phase transitions beginning: a cubic-paraelectric to a tetragonal-ferroelectric ''C'' (at the Curie temperature T c), after that to an orthorhombic-ferroelectric ''T ? O'' (at T T ? O), and lastly to a rhombohedral-ferroelectric ''O ? R'' (at T O ? R) resembling to those of pure Barium titanate (BaTiO 3 , BT). To clarify the dielectric phenomenon, the Curie-Weiss law is investigated. This method is used to describe the ferroparaelectric transition. The degree of disorder of the Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 was assessing via the modified Curie-Weiss law. The Raman spectrum was measured at room-temperature, and their variation related to the chemical composition, which affirmed the tetragonal structure for Ba 0.97 La 0.02 Ti 0.98 Nb 0.016 O 3 .
Journal of Inorganic and Organometallic Polymers and Materials, Jan 17, 2022
Barium zirconate titanate Ba(Zr y Ti 1Ày)O 3 (BZT, y = 0.2, 0.25, 0.30, 0.35) ceramics have been ... more Barium zirconate titanate Ba(Zr y Ti 1Ày)O 3 (BZT, y = 0.2, 0.25, 0.30, 0.35) ceramics have been prepared by a sol-gel process. The temperature dependence of dielectric permittivity of the ceramics has been investigated. The results show that the phase transition temperature T C (or T m) is suppressed with increasing Zr content. The degree of diffuseness of the phase transition is more pronounced for higher Zr content, implying the existence of a composition-induced diffuse phase transition of the ceramics with 0.20 6 y 6 0.35. For BZT ceramics with y > 0.25, a relaxor ferroelectric characteristic is observed. High tunability and figure of merit are obtained in BZT compositions investigated, which imply that these ceramics are promising materials for tunable capacitor applications.
Inorganic Chemistry Communications, Jul 1, 2021
Abstract In this work, we considered the notable effect of the substitution of Ti4+ by Nb5+ on th... more Abstract In this work, we considered the notable effect of the substitution of Ti4+ by Nb5+ on the structural, electric and dielectric properties of the Ba0.97La0.02Ti1−xNb4x/5O2 (BLTi1−xNb4x/5) compounds for x = 0.02, and 0.07. Our samples were synthesized via the molten-salt method. X-ray diffraction patterns revealed that both compounds have a tetragonal layered perovskite structure with P4/mmm space group. Electrical examination was cruelly focused by complex impedance spectroscopy in the frequency range (10 - 106 Hz). As the concentration of Nb increases, the real (') and imaginary ('') parts of the complex impedance have significantly decreased. The plot typically characterized by a single impedance semicircle for the two compounds, identified over the high and the medium frequencies. As well, at low frequency, followed by a linear section; was represented by the element Warburg. The conductivity decreased with the increase in the amount of niobium. The experimental data were fitted using Jonscher’s universal power law. The dielectric constant (er) has been changed appreciably from 0.5182x103 to 7.7905x103 with the increase in the amount of Nb. The impedance spectroscopic study revealed the presence of a semiconductor grain and an insulating grain boundary. These tow parameters support the internal barrier layer mechanism and are responsible for the high dielectric constant of these materials.
Journal of Inorganic and Organometallic Polymers and Materials, May 29, 2023
Engineering Analysis With Boundary Elements, Mar 1, 2023
Journal of Molecular Structure, Sep 1, 2022
Journal of Molecular Structure, Sep 1, 2022
Applied Physics A, Apr 25, 2022
Journal of Inorganic and Organometallic Polymers and Materials
Journal of Inorganic and Organometallic Polymers and Materials