Nilaya Mohanty - Academia.edu (original) (raw)
Papers by Nilaya Mohanty
Polymer Science Series B, 2015
arXiv (Cornell University), May 1, 2014
The 0.5(BiGd x Fe 1-x O 3)-0.5(PbZrO 3) composite was synthesized using a high temperature solid-... more The 0.5(BiGd x Fe 1-x O 3)-0.5(PbZrO 3) composite was synthesized using a high temperature solid-state reaction technique. Preliminary X-ray structural analysis confirms the formation of the composite. The dielectric constant and loss tangent have been studied. The hysteresis loop suggest that the material is lossy. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (10 2-10 6 Hz) at different temperatures for all samples. The Nyquist plot suggests the contribution of bulk effect as well as grain boundary effect and the bulk resistance deceases with rise in temperature for all samples. The electrical transport confirms the presence of hopping mechanism in the material. The dc conductivity increases with rise in temperature. The frequency variation of ac conductivity shows that the compound obeys Jonscher's universal power law and confirms the Small Polaron (SP) tunneling effect due to low activation energy for all samples. Temperature dependence of dc and ac conductivity indicates that electrical conduction in the materials are thermally activated process.
Advanced Materials Letters, 2013
The polycrystalline sample of 0.7(BiFeO 3)-0.3(PbTiO 3) [0.7(BFO)-0.3(PT)] was prepared by a high... more The polycrystalline sample of 0.7(BiFeO 3)-0.3(PbTiO 3) [0.7(BFO)-0.3(PT)] was prepared by a high temperature solid state reaction technique. Studies of structural analysis confirm the formation of the compound with rhombohedral structure at room temperature. The electrical properties (impedance, modulus and conductivity) of the material were analyzed using a complex impedance spectroscopy technique in a wide temperature (225-300 o C) and frequency (10 2-10 6 Hz) range. The studied material exhibits a significant contribution of grain (bulk) effect and non-Debye of relaxation process. The bulk resistance decreases with rise in temperature which exhibits negative temperature coefficient of resistance (NTCR) behavior. Electrical modulus study confirms the presence of bulk effect in the material. This compound also exhibits the temperature dependence of relaxation phenomena. The ac and dc conductivity of the materials were found to be increase with increase in temperature. The activation energy of the compound is found to be less than 1eV and suggests the conduction process is of mixed type (ionic-polaronic and singly-ionized oxygen ion vacancies).
Advanced Materials Letters, 2015
The Gd-modified BiFeO 3-PbTiO 3 composites i.e. 0.5BiGd x Fe 1-x O 3-0.5PbTiO 3 (BG x F 1-x-PT) w... more The Gd-modified BiFeO 3-PbTiO 3 composites i.e. 0.5BiGd x Fe 1-x O 3-0.5PbTiO 3 (BG x F 1-x-PT) with x=0.00, 0.05, 0.10, 0.15, 0.20, were prepared by mixed oxide method at high temperature. The structural study reveals that the composites showed tetragonal crystal structure at room temperature and tetragonality (c/a ratio) of composites decrease with increase in Gd concentration. The average crystallite size of the composites was found to be in the range of 30-89 nm. Surface morphology of the composites was studied by scanning electron microscopy (SEM). The Goldschmidt tolerance factors of the composites were found to be in the range of 0.989-0.976. The nature of Nyquist plot confirmed the presence of both bulk and grain boundary effects, and non-Debye type of relaxation process occur in the composites. The activation energy of the composites was found to be in the range 0.13-1.38eV. The analyses of ac conductivity data obey the universal agreement with Jonscher"s power law. Further, the explanation of conduction mechanism through correlated barrier hopping (CBH) model was discussed.
Journal of Rare Earths, 2015
0.5BiDy x Fe 1-x O 3-0.5PbTiO 3 (0.5BD x F 1-x-0.5PT) (x=0.00, 0.05, 0.10, 0.15, 0.20) multiferro... more 0.5BiDy x Fe 1-x O 3-0.5PbTiO 3 (0.5BD x F 1-x-0.5PT) (x=0.00, 0.05, 0.10, 0.15, 0.20) multiferroic composites were prepared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the materials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope (SEM). Frequency and temperature dependence of dielectric constant (ε r) and dielectric loss (tanδ) of 0.5BD x F 1-x-0.5PT were measured in a wide range of frequency (100 Hz to 1 MHz) and temperature (25 to 400 ºC). The analysis of the study showed that the ε r and tanδ decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium (Dy) showed increase in ε r in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of ε r for Dy modified 0.5BiFeO 3-0.5PbTiO 3 (0.5BF-0.5PT) compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance (NTCR) behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.
Acta Metallurgica Sinica (English Letters), 2015
The Lanthanum-doped bismuth ferrite-lead titanate compositions of 0.5(BiLa x Fe 1-x O 3)-0.5(PbTi... more The Lanthanum-doped bismuth ferrite-lead titanate compositions of 0.5(BiLa x Fe 1-x O 3)-0.5(PbTiO 3) (x = 0.05, 0.10, 0.15, 0.20) (BL x F 1-x-PT) were prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature. The lattice parameter c/a ratio decreases with increasing of La(x = 0.05-0.20) concentration of the composites. The effect of charge carrier/ion hopping mechanism, conductivity, relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range (10 2-10 6 Hz) at different temperatures. The nature of Nyquist plot confirms the presence of bulk effects only, and non-Debye type of relaxation processes occurs in the composites. The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials. The ac conductivity and dc conductivity of the materials were studied, and the activation energy found to be 0.81, 0.77, 0.76 and 0.74 eV for all compositions of x = 0.05-0.20 at different temperatures (200-300°C).
AIP Conference Proceedings, 2011
ABSTRACT The polycrystalline sample of LiSr2Nb5O15 (LSN) was prepared by a high temperature solid... more ABSTRACT The polycrystalline sample of LiSr2Nb5O15 (LSN) was prepared by a high temperature solid-state reaction technique. Studies of structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. X-ray studies reveal that the material has an orthorhombic structure at room temperature. Dielectric properties were measured over a wide range of temperature (28-500 °C) and frequency (102-106 Hz). Conductivity of the material increases with rise in temperature.
Journal of Advanced Ceramics, 2012
The polycrystalline sample of LiSr 2 Nb 5 O 15 (LSN) was prepared by a high-temperature solid sta... more The polycrystalline sample of LiSr 2 Nb 5 O 15 (LSN) was prepared by a high-temperature solid state reaction technique. The impedance parameters were studied using an impedance analyzer in a wide range of frequencies (10 2-10 6 Hz) at different temperatures (28-500 ℃). Nyquist plot reveals the presence of bulk effect only. The bulk resistance of the compound decreases with rise in temperature which shows the negative temperature coefficient of resistance (NTCR) like a semiconductor. The ac conductivity spectrum was found to obey Jonscher's universal power law. DC conductivity (bulk) with temperature demonstrates that the compound exhibits Arrhenius type of electrical conductivity and the activation energy found to be 0.97 eV.
Materials Science-Poland, 2014
The 0.5(BiGd 0.05 Fe 0.95 O 3)-0.5(PbZrO 3) composite was synthesized by means of a high temperat... more The 0.5(BiGd 0.05 Fe 0.95 O 3)-0.5(PbZrO 3) composite was synthesized by means of a high temperature solid-state reaction technique using high purity ingredients. Preliminary X-ray structural analysis confirms the formation of the composite. The dielectric constant and loss tangent have been studied. The impedance parameters have been measured using an impedance analyzer in a wide range of frequency (10 2-10 6 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect only and the bulk resistance decreases with a rise in temperature. Electrical impedance confirms the presence of grain effect and hopping mechanism in the electrical transport of the material. The dc conductivity increases with a rise of temperature. The frequency variation of ac conductivity shows that the compound obeys Jonscher's universal power law and from Jonscher's power law fit confirms the Small Polaron (SP) tunneling effect. Temperature dependence of dc and ac conductivity indicates that electrical conduction in the material is a thermally activated process.
Frontiers of Materials Science, 2013
The composite, 0.5(BiGd 0.15 Fe 0.85 O 3)-0.5(PbZrO 3), was synthesized using the solid-state rea... more The composite, 0.5(BiGd 0.15 Fe 0.85 O 3)-0.5(PbZrO 3), was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (10 2-10 6 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and σ dc were obtained by fitting ac conductivity data with Jonscher's universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and 1 MHz respectively in the temperature region of 110°C-350°C. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher's power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.
AIP Conference Proceedings, 2014
ABSTRACT 0.5BiGdxFe1-xO3-0.5PbTiO3 with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed ... more ABSTRACT 0.5BiGdxFe1-xO3-0.5PbTiO3 with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and studied that the materials show tetragonal structure at room temperature for all concentration of Gd. Studies of dielectric properties (∊r and tanδ) of the above compound at different frequencies in a wide range of temperature (25°-500°C) with an impedance analyser revealed that the dielectric constant increases with increase in Gd concentration as well temperature and the compound do not have any dielectric anomaly in the studied frequency and temperature range.
Journal of Materials Science: Materials in Electronics, 2013
The layered structure bismuth oxide, Ba 0.5 Sr 0.5 Bi 2 V 2 O 9 , was prepared using solid state ... more The layered structure bismuth oxide, Ba 0.5 Sr 0.5 Bi 2 V 2 O 9 , was prepared using solid state reaction technique. Room temperature X-ray diffraction study confirms the formation of the material with an orthorhombic crystal structure. The temperature dependent impedance parameters were investigated using an impedance analyzer in a wide range of frequencies (10 2-10 6 Hz) at different temperatures. The Nyquist plots reveal the presence of both grain and grain boundary effect above 275°C. The bulk resistance of the material decreases with rise in temperature which shows negative temperature coefficient resistance behavior like semiconductor. The variation of ac electrical conductivity (r ac) was measured, and the activation energy of the material found to be 0.36, 0.33, 0.34, 0.31 eV at 10, 50, 100 and 500 kHz respectively. Ac conductivity data were used to evaluate the density of states at Fermi level. From the dynamic light scattering and electrophoretic light scattering study, it is observed that the particle show excellent aqueous dispersion stability without any change in hydrodynamic size and zeta potential.
Polymer Science Series B, 2015
arXiv (Cornell University), May 1, 2014
The 0.5(BiGd x Fe 1-x O 3)-0.5(PbZrO 3) composite was synthesized using a high temperature solid-... more The 0.5(BiGd x Fe 1-x O 3)-0.5(PbZrO 3) composite was synthesized using a high temperature solid-state reaction technique. Preliminary X-ray structural analysis confirms the formation of the composite. The dielectric constant and loss tangent have been studied. The hysteresis loop suggest that the material is lossy. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (10 2-10 6 Hz) at different temperatures for all samples. The Nyquist plot suggests the contribution of bulk effect as well as grain boundary effect and the bulk resistance deceases with rise in temperature for all samples. The electrical transport confirms the presence of hopping mechanism in the material. The dc conductivity increases with rise in temperature. The frequency variation of ac conductivity shows that the compound obeys Jonscher's universal power law and confirms the Small Polaron (SP) tunneling effect due to low activation energy for all samples. Temperature dependence of dc and ac conductivity indicates that electrical conduction in the materials are thermally activated process.
Advanced Materials Letters, 2013
The polycrystalline sample of 0.7(BiFeO 3)-0.3(PbTiO 3) [0.7(BFO)-0.3(PT)] was prepared by a high... more The polycrystalline sample of 0.7(BiFeO 3)-0.3(PbTiO 3) [0.7(BFO)-0.3(PT)] was prepared by a high temperature solid state reaction technique. Studies of structural analysis confirm the formation of the compound with rhombohedral structure at room temperature. The electrical properties (impedance, modulus and conductivity) of the material were analyzed using a complex impedance spectroscopy technique in a wide temperature (225-300 o C) and frequency (10 2-10 6 Hz) range. The studied material exhibits a significant contribution of grain (bulk) effect and non-Debye of relaxation process. The bulk resistance decreases with rise in temperature which exhibits negative temperature coefficient of resistance (NTCR) behavior. Electrical modulus study confirms the presence of bulk effect in the material. This compound also exhibits the temperature dependence of relaxation phenomena. The ac and dc conductivity of the materials were found to be increase with increase in temperature. The activation energy of the compound is found to be less than 1eV and suggests the conduction process is of mixed type (ionic-polaronic and singly-ionized oxygen ion vacancies).
Advanced Materials Letters, 2015
The Gd-modified BiFeO 3-PbTiO 3 composites i.e. 0.5BiGd x Fe 1-x O 3-0.5PbTiO 3 (BG x F 1-x-PT) w... more The Gd-modified BiFeO 3-PbTiO 3 composites i.e. 0.5BiGd x Fe 1-x O 3-0.5PbTiO 3 (BG x F 1-x-PT) with x=0.00, 0.05, 0.10, 0.15, 0.20, were prepared by mixed oxide method at high temperature. The structural study reveals that the composites showed tetragonal crystal structure at room temperature and tetragonality (c/a ratio) of composites decrease with increase in Gd concentration. The average crystallite size of the composites was found to be in the range of 30-89 nm. Surface morphology of the composites was studied by scanning electron microscopy (SEM). The Goldschmidt tolerance factors of the composites were found to be in the range of 0.989-0.976. The nature of Nyquist plot confirmed the presence of both bulk and grain boundary effects, and non-Debye type of relaxation process occur in the composites. The activation energy of the composites was found to be in the range 0.13-1.38eV. The analyses of ac conductivity data obey the universal agreement with Jonscher"s power law. Further, the explanation of conduction mechanism through correlated barrier hopping (CBH) model was discussed.
Journal of Rare Earths, 2015
0.5BiDy x Fe 1-x O 3-0.5PbTiO 3 (0.5BD x F 1-x-0.5PT) (x=0.00, 0.05, 0.10, 0.15, 0.20) multiferro... more 0.5BiDy x Fe 1-x O 3-0.5PbTiO 3 (0.5BD x F 1-x-0.5PT) (x=0.00, 0.05, 0.10, 0.15, 0.20) multiferroic composites were prepared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the materials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope (SEM). Frequency and temperature dependence of dielectric constant (ε r) and dielectric loss (tanδ) of 0.5BD x F 1-x-0.5PT were measured in a wide range of frequency (100 Hz to 1 MHz) and temperature (25 to 400 ºC). The analysis of the study showed that the ε r and tanδ decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium (Dy) showed increase in ε r in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of ε r for Dy modified 0.5BiFeO 3-0.5PbTiO 3 (0.5BF-0.5PT) compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance (NTCR) behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.
Acta Metallurgica Sinica (English Letters), 2015
The Lanthanum-doped bismuth ferrite-lead titanate compositions of 0.5(BiLa x Fe 1-x O 3)-0.5(PbTi... more The Lanthanum-doped bismuth ferrite-lead titanate compositions of 0.5(BiLa x Fe 1-x O 3)-0.5(PbTiO 3) (x = 0.05, 0.10, 0.15, 0.20) (BL x F 1-x-PT) were prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature. The lattice parameter c/a ratio decreases with increasing of La(x = 0.05-0.20) concentration of the composites. The effect of charge carrier/ion hopping mechanism, conductivity, relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range (10 2-10 6 Hz) at different temperatures. The nature of Nyquist plot confirms the presence of bulk effects only, and non-Debye type of relaxation processes occurs in the composites. The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials. The ac conductivity and dc conductivity of the materials were studied, and the activation energy found to be 0.81, 0.77, 0.76 and 0.74 eV for all compositions of x = 0.05-0.20 at different temperatures (200-300°C).
AIP Conference Proceedings, 2011
ABSTRACT The polycrystalline sample of LiSr2Nb5O15 (LSN) was prepared by a high temperature solid... more ABSTRACT The polycrystalline sample of LiSr2Nb5O15 (LSN) was prepared by a high temperature solid-state reaction technique. Studies of structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. X-ray studies reveal that the material has an orthorhombic structure at room temperature. Dielectric properties were measured over a wide range of temperature (28-500 °C) and frequency (102-106 Hz). Conductivity of the material increases with rise in temperature.
Journal of Advanced Ceramics, 2012
The polycrystalline sample of LiSr 2 Nb 5 O 15 (LSN) was prepared by a high-temperature solid sta... more The polycrystalline sample of LiSr 2 Nb 5 O 15 (LSN) was prepared by a high-temperature solid state reaction technique. The impedance parameters were studied using an impedance analyzer in a wide range of frequencies (10 2-10 6 Hz) at different temperatures (28-500 ℃). Nyquist plot reveals the presence of bulk effect only. The bulk resistance of the compound decreases with rise in temperature which shows the negative temperature coefficient of resistance (NTCR) like a semiconductor. The ac conductivity spectrum was found to obey Jonscher's universal power law. DC conductivity (bulk) with temperature demonstrates that the compound exhibits Arrhenius type of electrical conductivity and the activation energy found to be 0.97 eV.
Materials Science-Poland, 2014
The 0.5(BiGd 0.05 Fe 0.95 O 3)-0.5(PbZrO 3) composite was synthesized by means of a high temperat... more The 0.5(BiGd 0.05 Fe 0.95 O 3)-0.5(PbZrO 3) composite was synthesized by means of a high temperature solid-state reaction technique using high purity ingredients. Preliminary X-ray structural analysis confirms the formation of the composite. The dielectric constant and loss tangent have been studied. The impedance parameters have been measured using an impedance analyzer in a wide range of frequency (10 2-10 6 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect only and the bulk resistance decreases with a rise in temperature. Electrical impedance confirms the presence of grain effect and hopping mechanism in the electrical transport of the material. The dc conductivity increases with a rise of temperature. The frequency variation of ac conductivity shows that the compound obeys Jonscher's universal power law and from Jonscher's power law fit confirms the Small Polaron (SP) tunneling effect. Temperature dependence of dc and ac conductivity indicates that electrical conduction in the material is a thermally activated process.
Frontiers of Materials Science, 2013
The composite, 0.5(BiGd 0.15 Fe 0.85 O 3)-0.5(PbZrO 3), was synthesized using the solid-state rea... more The composite, 0.5(BiGd 0.15 Fe 0.85 O 3)-0.5(PbZrO 3), was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (10 2-10 6 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and σ dc were obtained by fitting ac conductivity data with Jonscher's universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and 1 MHz respectively in the temperature region of 110°C-350°C. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher's power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.
AIP Conference Proceedings, 2014
ABSTRACT 0.5BiGdxFe1-xO3-0.5PbTiO3 with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed ... more ABSTRACT 0.5BiGdxFe1-xO3-0.5PbTiO3 with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and studied that the materials show tetragonal structure at room temperature for all concentration of Gd. Studies of dielectric properties (∊r and tanδ) of the above compound at different frequencies in a wide range of temperature (25°-500°C) with an impedance analyser revealed that the dielectric constant increases with increase in Gd concentration as well temperature and the compound do not have any dielectric anomaly in the studied frequency and temperature range.
Journal of Materials Science: Materials in Electronics, 2013
The layered structure bismuth oxide, Ba 0.5 Sr 0.5 Bi 2 V 2 O 9 , was prepared using solid state ... more The layered structure bismuth oxide, Ba 0.5 Sr 0.5 Bi 2 V 2 O 9 , was prepared using solid state reaction technique. Room temperature X-ray diffraction study confirms the formation of the material with an orthorhombic crystal structure. The temperature dependent impedance parameters were investigated using an impedance analyzer in a wide range of frequencies (10 2-10 6 Hz) at different temperatures. The Nyquist plots reveal the presence of both grain and grain boundary effect above 275°C. The bulk resistance of the material decreases with rise in temperature which shows negative temperature coefficient resistance behavior like semiconductor. The variation of ac electrical conductivity (r ac) was measured, and the activation energy of the material found to be 0.36, 0.33, 0.34, 0.31 eV at 10, 50, 100 and 500 kHz respectively. Ac conductivity data were used to evaluate the density of states at Fermi level. From the dynamic light scattering and electrophoretic light scattering study, it is observed that the particle show excellent aqueous dispersion stability without any change in hydrodynamic size and zeta potential.