R N P Choudhary - Academia.edu (original) (raw)
Papers by R N P Choudhary
Journal of Materials Science, 1987
The Raman and infrared spectra of polycrystalline samples TIH2AsO 4, TID2AsO 4, TIH2PO 4 and TID2... more The Raman and infrared spectra of polycrystalline samples TIH2AsO 4, TID2AsO 4, TIH2PO 4 and TID2PO 4 have been investigated at 300 K in the frequency ranges 0 to 4000 and 200 to 4000cm-1 respectively. The assignment of lattice, internal, and OH group vibrations has been approximated in terms of symmetry species. Although all the vibrations follow more or less the space group symmetry, the internal vibrations do not completely fulfill the requirements of the symmetry rule. The isotope effect was observed prominently on both compounds in Raman and infrared spectra. An attempt has been made to assign and explain the results.
Journal of Advanced Dielectrics, 2014
The polycrystalline samples of Bi 1-x Gd x FeO 3 (x = 0, 0.1, and 0.2) multiferroic oxides have b... more The polycrystalline samples of Bi 1-x Gd x FeO 3 (x = 0, 0.1, and 0.2) multiferroic oxides have been synthesized by a solid-state reaction/mixed oxide technique. The preliminary X-ray structural analysis with room temperature diffraction data confirmed the formation of single-phase systems. Study of room temperature scanning electron micrograph (SEM) of the surface of the above samples exhibits a uniform distribution of plate- and rod-shaped grains throughout the sample surface with less porosity. The dielectric behavior of the materials was studied in a wide range of frequency (1 kHz–1 MHz) and temperature (30–400°C). The nature of temperature dependence of dc conductivity confirms the Arrhenius behavior of the materials. The frequency–temperature dependence of ac conductivity suggests that the material obeys Jonscher's universal power law. An increase in Gd -content results in the enhancement of spontaneous magnetization BiFeO 3 (BFO) due to the collapse of spin cycloid struct...
Research Letters in Materials Science, 2007
The polycrystalline samples ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) were prepared by low-temperature, (i... more The polycrystalline samples ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) were prepared by low-temperature, (i.e., at650∘C) solid-state reaction technique. The preparation conditions have been optimized using thermogravimetry analysis (TGA) technique. X-ray diffraction (XRD) studies of the compounds showed the formation of a single-phase orthorhombic crystal structure at room temperature. Studies of dielectric properties (ɛrand tanδ) of the compounds at frequencies 10, 100, and 1000 kHz in a wide temperature range (room temperature–500∘C) exhibit ferroelectric phase transitions at132∘Cfor NPDWTV and at122∘Cfor NPPWTV of diffuse type. Ferroelectric properties of the materials are confirmed by polarization study.
Advances in Applied Ceramics, 2005
The electrical properties of polycrystalline Pb 2 Sb 3 DyTi 5 O 18 were investigated by complex i... more The electrical properties of polycrystalline Pb 2 Sb 3 DyTi 5 O 18 were investigated by complex impedance spectroscopy. The dielectric relaxation was found to be of polydispersive non-Debye type, and relaxation frequency shifts to higher frequencies with increasing temperature. Evidence of temperature dependent electrical relaxation phenomena as well as the negative temperature coefficient of resistance (NTCR) character of the sample have also been observed. The ac conductivity obeys the universal power law and dispersion in conductivity was observed in the lower frequency region. Also, the frequency dependent ac conductivity at different temperatures indicated that the conduction process is thermally activated. The activation energy was estimated to be 0. 62 eV from the temperature variation of dc conductivity.
AIP Conference Proceedings, 2008
The polycrystalline samples of BaTi1-xMnxO3 (BTM) ferroelectric ceramics with x = 0, 0.04, 0.07, ... more The polycrystalline samples of BaTi1-xMnxO3 (BTM) ferroelectric ceramics with x = 0, 0.04, 0.07, 0.1 has been prepared using a solid-state reaction technique. Preliminary structural studies using X-ray diffraction technique at room temperature suggests that compounds have single phase with the orthorhombic crystal system. The scanning electron micrographs show uniform grain distribution throughout the surface of the samples. Dielectric properties
Express Polymer Letters, 2008
Structural, thermal and electrical behavior of polymer-clay nanocomposite electrolytes consisting... more Structural, thermal and electrical behavior of polymer-clay nanocomposite electrolytes consisting of polymer (polyethylene oxide (PEO)) and NaI as salt with different concentrations of organically modified Na + montmorillonite (DMMT) filler have been investigated. The formation of nanocomposites and changes in the structural properties of the materials were investigated by X-ray diffraction (XRD) analysis. Complex impedance analysis shows the existence of bulk and material-electrode interface properties of the composites. The relative dielectric constant (εr) decreases with increase in frequency in the low frequency region whereas frequency independent behavior is observed in the high frequency region. The electrical modulus representation shows a loss feature in the imaginary component. The relaxation associated with this feature shows a stretched exponential decay. Studies of frequency dependence of dielectric and modulus formalism suggest that the ionic and polymer segmental motion are strongly coupled manifeasting as peak in the modulus (M″) spectra with no corresponding feature in dielectric spectra. The frequency dependence of ac (alternating current) conductivity obeys Jonscher power law feature in the high frequency region, where as the low frequency dispersion indicating the presence of electrode polarization effect in the materials.
Physica Status Solidi (a), 1987
The temperature and frequency dependence of dielectric properties for TID2PO4 is investigated at ... more The temperature and frequency dependence of dielectric properties for TID2PO4 is investigated at atmospheric pressure. A dielectric anomaly is observed at 353 K. The thermal properties (DSC and DTA) of TID2PO4 are studied from room temperature to 450 K. A thermal anomaly is observed at 353 K in DTA measurements, also. The dielectric hysteresis loop is studied at room temperature. The results show that TID2PO4 is antiferroelectric in the room temperature phase. Bei Atmospharendruck werden die Temperatur- und Frequenzabhangigkeit der dielektrisehen Eigensehaften von TID2PO4 untersucht. Bei 353 K wird eine dielektrische Anomalie beobachtet. Die thermischen Eigenschaften (DSC und DTA) von TID2PO4 werden zwischen Zimmertemperatur und 450 K untersucht. In den DTA-Messungen wird ebenfalls bei 353 K eine thermisehe Anomalie beobachtet. Dielektrische Hystereseschleifen werden bei Zimmertemperatur untersucht. Die Ergebnisse zeigen, das TID2PO4 in der Raumtemperaturphase antiferroelektrisch ist.
Physica B: Condensed Matter, 2007
The polycrystalline sample of Li2BiV5O15 was prepared by a mixed-oxide method, relatively at low ... more The polycrystalline sample of Li2BiV5O15 was prepared by a mixed-oxide method, relatively at low temperature (i.e., 550°C). Room temperature XRD pattern confirms the formation of the compound with an orthorhombic crystal system. Studies of dielectric properties show that the compound exhibits an anomaly at 416°C (usually called transition temperature) at 50 and 100kHz, with diffuse-type phase transition. The electrical parameters
Journal of Materials Science: Materials in Electronics, 2013
ABSTRACT This paper reports about the double phase transition (at 315 and 366 °C) in the polycrys... more ABSTRACT This paper reports about the double phase transition (at 315 and 366 °C) in the polycrystalline sample of K2Pb2Sm2W2Ti4Nb4O30 prepared by a high-temperature solid-state reaction technique. The calcination temperature was decided based on thermogravimetry analysis. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The surface morphology recorded by scanning electron microscope exhibits a uniform grain distribution with high density. Detailed studies on the nature of variation (1) of dielectric parameters with temperature, and (2) polarization with temperature confirmed the existence of ferroelectricity in the material at room temperature. The temperature dependence of dc conductivity shows a typical Arrhenius behavior. The frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit, thus making it useful for pyroelectric sensors.
Journal of Materials Science Letters, 1988
Journal of Materials Science, 2004
Zr-modified Sr 5 LaTi 3 Nb 7 O 30 compound was prepared by a high-temperature solid-state reactio... more Zr-modified Sr 5 LaTi 3 Nb 7 O 30 compound was prepared by a high-temperature solid-state reaction technique. X-ray structural analysis confirmed the formation of compound in an orthorhombic system at room temperature. Detailed studies of the dielectric parameters (dielectric constant and tangent loss) as a function of frequency (1-100 kHz) at different temperature (150 to 650 K) were carried out. It was found that as Zr +4 concentration increases in Sr 5 LaTi 3−x Zr x Nb 7 O 30 , the value of dielectric constant decreases. These compounds show ferroelectric-paraelectric phase transition of diffuse type at 283, 305 and 320 K for x = 0, 1 and 2 respectively. The transition temperature (T c) shifts towards higher temperature and maximum dielectric constant value (ε max) decreases with increasing Zr +4 concentration for x = 0 to x = 2. When Ti +4 cations were completely replaced by Zr +4 cations (i.e., Sr 5 LaZr 3 Nb 7 O 30), the compound does not show any phase transition. Impedance-spectroscopic studies provided an insight into the electrical properties and understanding of relaxation behavior of the material. Measurement of electrical conductivity as a function of temperature suggests that the compounds have a negative temperature coefficient of resistivity (NTCR) with a typical semiconductor behavior.
Ferroelectrics, 2005
... Soc. 23(8), 1337 (2003). Page 12. 86/[416] RNP Choudhary et al. 2. LB Kong, J. Ma, RF Zhang, ... more ... Soc. 23(8), 1337 (2003). Page 12. 86/[416] RNP Choudhary et al. 2. LB Kong, J. Ma, RF Zhang, and TS Zhang, J. Alloys. Comps. 339, 167 (2002). ... Chem. and Phys. 80, 29 (2003). 15. Om Prakash, D. Kumar, K. K Shrivastava, and RK Dwivedi, J. Mat. Sc., 36(24), 5805 (2001). 16. ...
physica status solidi (a), 2004
Polycrystalline Na 2 W 2 O 7 (anhydrous) was prepared by a solid-state reaction technique. The fo... more Polycrystalline Na 2 W 2 O 7 (anhydrous) was prepared by a solid-state reaction technique. The formation of the compound has been confirmed by X-ray powder diffraction studies and Raman spectroscopy. The unit cell structure of the material has been found to be orthorhombic of the Cmca space group. Complex impedance analysis of the material indicates the electrical conduction to be due only to the grain interior up to a temperature of 300 °C. Above 300 °C the contribution of the grain boundary to electrical conduction is more evident. The grain boundary resistance is found to decrease with increasing temperature. Impedance results also indicate that the material exhibits a negative temperature coefficient of resistance. The electrical processes in the material show temperature-dependent relaxation phenomena. The electrical conduction in the material is a thermally activated process governed by the release of space charge in close agreement with the observations made from impedance spectrum analysis. The dc conductivity of the material as evaluated from the complex impedance spectrum is observed to attain a maximum value of 1.16 × 10-6 S cm-1 at 425 °C. This is a very large increase, nearly four orders of magnitude, when compared with the room temperature conductivity of the material (3.99 × 10-10 S cm-1).
![Research paper thumbnail of Dielectric, Electrical and Magnetic Properties of PbZr[sub 0.53]Ti[sub 0.47] O[sub 3] -Ni[sub 0.65]Zn[sub 0.35]Fe[sub 2]O[sub 4] Multiferroic Composite](https://attachments.academia-assets.com/94937402/thumbnails/1.jpg)
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Journal of Materials Science Letters, 2000
The lead zirconate titanate solid solutions (PZT) of ABO 3 type of perovskite (A = mono-or divale... more The lead zirconate titanate solid solutions (PZT) of ABO 3 type of perovskite (A = mono-or divalent ions; B = tri-hexavalent ions) have become the most widely used piezoelectric ceramics. Because of their industrial importance, they have been the subject of extensive research. In these solid solutions A-sites are occupied by Pb 2+ ions and Zr 4+ and Ti 4+ ions are accommodated on the B-sites. The influence of various substitutions in the A and B sites of the PZT unit cell has been studied by numerous investigators in order to enhance the properties of the materials for device applications [1-3]. The majority of the substitutions are classified as isovalent, supervalent, and subvalent on the basis of their valency and position in the unit cell. In ferroelectric materials, when there are more than two kinds of ions in the same sublattice of the crystal, a random distribution of ions causes the composition to fluctuate, and the phase transition of the materials will be diffused. This characteristic has been found in lanthanum modified PZT ceramics (PLZT), which are widely and effectively used in many devices [4]. Besides the composition, the powder sample fabrication techniques are also quite important to achieve the desired properties of the ceramics. For instance, the conventionally prepared cold pressed sintered pellets of PLZT (9/65/35) ceramics are opaque, whereas the hot pressed ones are transparent [5]. Of the many fabrication procedures, the sol-gel route provides good homogeneity of the solid solution and yields finer particles [6]. The end results of the products are also known to depend on the sintering temperature [7]. In view of the above importance of PZT, we have synthesized the complex PZT compound or solid solution by a sol-gel route and have studied the sintering temperature effects on its structural and dielectric properties. The GR grade acetates of lead and lanthanum, titanium isopropoxide and zirconyl acetate derived from zirconyl nitrate were used in the proper stoichiometry for the preparation of Pb 0.91 La 0.09 (Zr 0.65 Ti 0.35) 0.9775 O 3 ceramics through a sol-gel route [8]. The resultant mixture obtained by this process was dried at 60 • C in an air oven to form a resin. The powders were then calcined at different temperatures (viz., 400 • C, 600 • C
Physica Status Solidi (a), 1987
The dielectric properties of polycrystalline samples of SmAsO, and YAsO, are measured in the freq... more The dielectric properties of polycrystalline samples of SmAsO, and YAsO, are measured in the frequency range 1 0 2 to lo4 Hz and in the temperature region 295 to 473 K. The dielectric dispersion both, a t room temperature and higher temperature is attributed to space charge polarisation. No dielectric anomaly is observed in the said temperature region. Moderately large value of the activation energy calculated from the conductivity versus temperature plots suggests that the conductivity may be associated with the ions. Die diclektrischen Eigenschaften von polykristallinen Proben von SmAsO, und YAsO, werden im Frequenzbereich von lo2 bis lo3 Hz und im Temperaturbereich 295 bis 473 K gemessen. Die diclektrischo Dispersion sowohl bei Zimmerteniperatur als auch bei hoheren Temperaturen wird der R,aumladungspolarisation zugeordnet. I m angegebenen Teniperaturbereich wird keine dielektrische Anomalie beobachtet. Mafiig groSe Werte der Aktivierungsenergie, die aus der Auftragung dcr Leitf&higlteit fiber der Temperatur berechnet werden, weisen darauf hin, da13 die Leitfahigkcit mit Ionen verkniipft werden kann.
Materials Science and Engineering: B, 2003
Polycrystalline samples of [Pb 0.92 (La 1(z Bi z) 0.08 ][Zr 0.60 Ti 0.40 ] 0.98 O 3 (z 0/0.0, 0.3... more Polycrystalline samples of [Pb 0.92 (La 1(z Bi z) 0.08 ][Zr 0.60 Ti 0.40 ] 0.98 O 3 (z 0/0.0, 0.3, 0.6, 0.9, 1) (PLBZT) were synthesized using a high-temperature solid-state reaction technique. The formation of the PLBZT compounds in a particular crystallographic phase as a function of Bi concentration was checked through X-ray diffraction (XRD). S.E.M. study of PLBZT with higher magnification and resolution shows the uniform distribution of particles/grains on the surface of the samples. Dielectric constant and tangent loss of the samples in wide temperature and frequency range provided the nature of phase transition. The diffuse phase transition was observed for higher z. An increase in permittivity maxima temperature (i.e. the transition temperature) was also observed with increasing Bi concentration. The values of resistivity of all the samples are very high (10 9 V-cm).
Journal of Materials Science, 2004
Detailed studies of structural, dielectric, and electrical characteristics of a precursor solutio... more Detailed studies of structural, dielectric, and electrical characteristics of a precursor solution method synthesized, bismuth and lead titanate modified manganese titanate (MnTiO 3) are reported in this communication. Analysis of X-ray diffraction data shows that MnTiO 3 goes through a structural change on the addition of Bi and PbTiO 3 (PT). At room temperature, MnTiO 3 has a rhombohedral crystal system, which changes to an orthorhombic crystal system with the addition of bismuth in it (i.e., BiMn 1/2 Ti 1/2 O 3 = BMT). On further addition of PT in BMT (i.e., 0.5 BiMn 1/2 Ti 1/2 O 3-0.5PbTiO 3), a stable perovskite structure with tetragonal symmetry was obtained. It is found that the addition of bismuth and lead titanate effectively reduces the grain size, and hence enhances the relative permittivity of the compound. It is further found that ferroelectricity can be induced in a non-ferroelectric MnTiO 3 on the addition of Bi and PbTiO 3 in it. However, the addition of bismuth and lead titanate increases the leakage current density of the compound.
Journal of Materials Science, 2004
Journal of Materials Science, 1987
The Raman and infrared spectra of polycrystalline samples TIH2AsO 4, TID2AsO 4, TIH2PO 4 and TID2... more The Raman and infrared spectra of polycrystalline samples TIH2AsO 4, TID2AsO 4, TIH2PO 4 and TID2PO 4 have been investigated at 300 K in the frequency ranges 0 to 4000 and 200 to 4000cm-1 respectively. The assignment of lattice, internal, and OH group vibrations has been approximated in terms of symmetry species. Although all the vibrations follow more or less the space group symmetry, the internal vibrations do not completely fulfill the requirements of the symmetry rule. The isotope effect was observed prominently on both compounds in Raman and infrared spectra. An attempt has been made to assign and explain the results.
Journal of Advanced Dielectrics, 2014
The polycrystalline samples of Bi 1-x Gd x FeO 3 (x = 0, 0.1, and 0.2) multiferroic oxides have b... more The polycrystalline samples of Bi 1-x Gd x FeO 3 (x = 0, 0.1, and 0.2) multiferroic oxides have been synthesized by a solid-state reaction/mixed oxide technique. The preliminary X-ray structural analysis with room temperature diffraction data confirmed the formation of single-phase systems. Study of room temperature scanning electron micrograph (SEM) of the surface of the above samples exhibits a uniform distribution of plate- and rod-shaped grains throughout the sample surface with less porosity. The dielectric behavior of the materials was studied in a wide range of frequency (1 kHz–1 MHz) and temperature (30–400°C). The nature of temperature dependence of dc conductivity confirms the Arrhenius behavior of the materials. The frequency–temperature dependence of ac conductivity suggests that the material obeys Jonscher's universal power law. An increase in Gd -content results in the enhancement of spontaneous magnetization BiFeO 3 (BFO) due to the collapse of spin cycloid struct...
Research Letters in Materials Science, 2007
The polycrystalline samples ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) were prepared by low-temperature, (i... more The polycrystalline samples ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) were prepared by low-temperature, (i.e., at650∘C) solid-state reaction technique. The preparation conditions have been optimized using thermogravimetry analysis (TGA) technique. X-ray diffraction (XRD) studies of the compounds showed the formation of a single-phase orthorhombic crystal structure at room temperature. Studies of dielectric properties (ɛrand tanδ) of the compounds at frequencies 10, 100, and 1000 kHz in a wide temperature range (room temperature–500∘C) exhibit ferroelectric phase transitions at132∘Cfor NPDWTV and at122∘Cfor NPPWTV of diffuse type. Ferroelectric properties of the materials are confirmed by polarization study.
Advances in Applied Ceramics, 2005
The electrical properties of polycrystalline Pb 2 Sb 3 DyTi 5 O 18 were investigated by complex i... more The electrical properties of polycrystalline Pb 2 Sb 3 DyTi 5 O 18 were investigated by complex impedance spectroscopy. The dielectric relaxation was found to be of polydispersive non-Debye type, and relaxation frequency shifts to higher frequencies with increasing temperature. Evidence of temperature dependent electrical relaxation phenomena as well as the negative temperature coefficient of resistance (NTCR) character of the sample have also been observed. The ac conductivity obeys the universal power law and dispersion in conductivity was observed in the lower frequency region. Also, the frequency dependent ac conductivity at different temperatures indicated that the conduction process is thermally activated. The activation energy was estimated to be 0. 62 eV from the temperature variation of dc conductivity.
AIP Conference Proceedings, 2008
The polycrystalline samples of BaTi1-xMnxO3 (BTM) ferroelectric ceramics with x = 0, 0.04, 0.07, ... more The polycrystalline samples of BaTi1-xMnxO3 (BTM) ferroelectric ceramics with x = 0, 0.04, 0.07, 0.1 has been prepared using a solid-state reaction technique. Preliminary structural studies using X-ray diffraction technique at room temperature suggests that compounds have single phase with the orthorhombic crystal system. The scanning electron micrographs show uniform grain distribution throughout the surface of the samples. Dielectric properties
Express Polymer Letters, 2008
Structural, thermal and electrical behavior of polymer-clay nanocomposite electrolytes consisting... more Structural, thermal and electrical behavior of polymer-clay nanocomposite electrolytes consisting of polymer (polyethylene oxide (PEO)) and NaI as salt with different concentrations of organically modified Na + montmorillonite (DMMT) filler have been investigated. The formation of nanocomposites and changes in the structural properties of the materials were investigated by X-ray diffraction (XRD) analysis. Complex impedance analysis shows the existence of bulk and material-electrode interface properties of the composites. The relative dielectric constant (εr) decreases with increase in frequency in the low frequency region whereas frequency independent behavior is observed in the high frequency region. The electrical modulus representation shows a loss feature in the imaginary component. The relaxation associated with this feature shows a stretched exponential decay. Studies of frequency dependence of dielectric and modulus formalism suggest that the ionic and polymer segmental motion are strongly coupled manifeasting as peak in the modulus (M″) spectra with no corresponding feature in dielectric spectra. The frequency dependence of ac (alternating current) conductivity obeys Jonscher power law feature in the high frequency region, where as the low frequency dispersion indicating the presence of electrode polarization effect in the materials.
Physica Status Solidi (a), 1987
The temperature and frequency dependence of dielectric properties for TID2PO4 is investigated at ... more The temperature and frequency dependence of dielectric properties for TID2PO4 is investigated at atmospheric pressure. A dielectric anomaly is observed at 353 K. The thermal properties (DSC and DTA) of TID2PO4 are studied from room temperature to 450 K. A thermal anomaly is observed at 353 K in DTA measurements, also. The dielectric hysteresis loop is studied at room temperature. The results show that TID2PO4 is antiferroelectric in the room temperature phase. Bei Atmospharendruck werden die Temperatur- und Frequenzabhangigkeit der dielektrisehen Eigensehaften von TID2PO4 untersucht. Bei 353 K wird eine dielektrische Anomalie beobachtet. Die thermischen Eigenschaften (DSC und DTA) von TID2PO4 werden zwischen Zimmertemperatur und 450 K untersucht. In den DTA-Messungen wird ebenfalls bei 353 K eine thermisehe Anomalie beobachtet. Dielektrische Hystereseschleifen werden bei Zimmertemperatur untersucht. Die Ergebnisse zeigen, das TID2PO4 in der Raumtemperaturphase antiferroelektrisch ist.
Physica B: Condensed Matter, 2007
The polycrystalline sample of Li2BiV5O15 was prepared by a mixed-oxide method, relatively at low ... more The polycrystalline sample of Li2BiV5O15 was prepared by a mixed-oxide method, relatively at low temperature (i.e., 550°C). Room temperature XRD pattern confirms the formation of the compound with an orthorhombic crystal system. Studies of dielectric properties show that the compound exhibits an anomaly at 416°C (usually called transition temperature) at 50 and 100kHz, with diffuse-type phase transition. The electrical parameters
Journal of Materials Science: Materials in Electronics, 2013
ABSTRACT This paper reports about the double phase transition (at 315 and 366 °C) in the polycrys... more ABSTRACT This paper reports about the double phase transition (at 315 and 366 °C) in the polycrystalline sample of K2Pb2Sm2W2Ti4Nb4O30 prepared by a high-temperature solid-state reaction technique. The calcination temperature was decided based on thermogravimetry analysis. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The surface morphology recorded by scanning electron microscope exhibits a uniform grain distribution with high density. Detailed studies on the nature of variation (1) of dielectric parameters with temperature, and (2) polarization with temperature confirmed the existence of ferroelectricity in the material at room temperature. The temperature dependence of dc conductivity shows a typical Arrhenius behavior. The frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit, thus making it useful for pyroelectric sensors.
Journal of Materials Science Letters, 1988
Journal of Materials Science, 2004
Zr-modified Sr 5 LaTi 3 Nb 7 O 30 compound was prepared by a high-temperature solid-state reactio... more Zr-modified Sr 5 LaTi 3 Nb 7 O 30 compound was prepared by a high-temperature solid-state reaction technique. X-ray structural analysis confirmed the formation of compound in an orthorhombic system at room temperature. Detailed studies of the dielectric parameters (dielectric constant and tangent loss) as a function of frequency (1-100 kHz) at different temperature (150 to 650 K) were carried out. It was found that as Zr +4 concentration increases in Sr 5 LaTi 3−x Zr x Nb 7 O 30 , the value of dielectric constant decreases. These compounds show ferroelectric-paraelectric phase transition of diffuse type at 283, 305 and 320 K for x = 0, 1 and 2 respectively. The transition temperature (T c) shifts towards higher temperature and maximum dielectric constant value (ε max) decreases with increasing Zr +4 concentration for x = 0 to x = 2. When Ti +4 cations were completely replaced by Zr +4 cations (i.e., Sr 5 LaZr 3 Nb 7 O 30), the compound does not show any phase transition. Impedance-spectroscopic studies provided an insight into the electrical properties and understanding of relaxation behavior of the material. Measurement of electrical conductivity as a function of temperature suggests that the compounds have a negative temperature coefficient of resistivity (NTCR) with a typical semiconductor behavior.
Ferroelectrics, 2005
... Soc. 23(8), 1337 (2003). Page 12. 86/[416] RNP Choudhary et al. 2. LB Kong, J. Ma, RF Zhang, ... more ... Soc. 23(8), 1337 (2003). Page 12. 86/[416] RNP Choudhary et al. 2. LB Kong, J. Ma, RF Zhang, and TS Zhang, J. Alloys. Comps. 339, 167 (2002). ... Chem. and Phys. 80, 29 (2003). 15. Om Prakash, D. Kumar, K. K Shrivastava, and RK Dwivedi, J. Mat. Sc., 36(24), 5805 (2001). 16. ...
physica status solidi (a), 2004
Polycrystalline Na 2 W 2 O 7 (anhydrous) was prepared by a solid-state reaction technique. The fo... more Polycrystalline Na 2 W 2 O 7 (anhydrous) was prepared by a solid-state reaction technique. The formation of the compound has been confirmed by X-ray powder diffraction studies and Raman spectroscopy. The unit cell structure of the material has been found to be orthorhombic of the Cmca space group. Complex impedance analysis of the material indicates the electrical conduction to be due only to the grain interior up to a temperature of 300 °C. Above 300 °C the contribution of the grain boundary to electrical conduction is more evident. The grain boundary resistance is found to decrease with increasing temperature. Impedance results also indicate that the material exhibits a negative temperature coefficient of resistance. The electrical processes in the material show temperature-dependent relaxation phenomena. The electrical conduction in the material is a thermally activated process governed by the release of space charge in close agreement with the observations made from impedance spectrum analysis. The dc conductivity of the material as evaluated from the complex impedance spectrum is observed to attain a maximum value of 1.16 × 10-6 S cm-1 at 425 °C. This is a very large increase, nearly four orders of magnitude, when compared with the room temperature conductivity of the material (3.99 × 10-10 S cm-1).
Journal of Materials Science Letters, 2000
The lead zirconate titanate solid solutions (PZT) of ABO 3 type of perovskite (A = mono-or divale... more The lead zirconate titanate solid solutions (PZT) of ABO 3 type of perovskite (A = mono-or divalent ions; B = tri-hexavalent ions) have become the most widely used piezoelectric ceramics. Because of their industrial importance, they have been the subject of extensive research. In these solid solutions A-sites are occupied by Pb 2+ ions and Zr 4+ and Ti 4+ ions are accommodated on the B-sites. The influence of various substitutions in the A and B sites of the PZT unit cell has been studied by numerous investigators in order to enhance the properties of the materials for device applications [1-3]. The majority of the substitutions are classified as isovalent, supervalent, and subvalent on the basis of their valency and position in the unit cell. In ferroelectric materials, when there are more than two kinds of ions in the same sublattice of the crystal, a random distribution of ions causes the composition to fluctuate, and the phase transition of the materials will be diffused. This characteristic has been found in lanthanum modified PZT ceramics (PLZT), which are widely and effectively used in many devices [4]. Besides the composition, the powder sample fabrication techniques are also quite important to achieve the desired properties of the ceramics. For instance, the conventionally prepared cold pressed sintered pellets of PLZT (9/65/35) ceramics are opaque, whereas the hot pressed ones are transparent [5]. Of the many fabrication procedures, the sol-gel route provides good homogeneity of the solid solution and yields finer particles [6]. The end results of the products are also known to depend on the sintering temperature [7]. In view of the above importance of PZT, we have synthesized the complex PZT compound or solid solution by a sol-gel route and have studied the sintering temperature effects on its structural and dielectric properties. The GR grade acetates of lead and lanthanum, titanium isopropoxide and zirconyl acetate derived from zirconyl nitrate were used in the proper stoichiometry for the preparation of Pb 0.91 La 0.09 (Zr 0.65 Ti 0.35) 0.9775 O 3 ceramics through a sol-gel route [8]. The resultant mixture obtained by this process was dried at 60 • C in an air oven to form a resin. The powders were then calcined at different temperatures (viz., 400 • C, 600 • C
Physica Status Solidi (a), 1987
The dielectric properties of polycrystalline samples of SmAsO, and YAsO, are measured in the freq... more The dielectric properties of polycrystalline samples of SmAsO, and YAsO, are measured in the frequency range 1 0 2 to lo4 Hz and in the temperature region 295 to 473 K. The dielectric dispersion both, a t room temperature and higher temperature is attributed to space charge polarisation. No dielectric anomaly is observed in the said temperature region. Moderately large value of the activation energy calculated from the conductivity versus temperature plots suggests that the conductivity may be associated with the ions. Die diclektrischen Eigenschaften von polykristallinen Proben von SmAsO, und YAsO, werden im Frequenzbereich von lo2 bis lo3 Hz und im Temperaturbereich 295 bis 473 K gemessen. Die diclektrischo Dispersion sowohl bei Zimmerteniperatur als auch bei hoheren Temperaturen wird der R,aumladungspolarisation zugeordnet. I m angegebenen Teniperaturbereich wird keine dielektrische Anomalie beobachtet. Mafiig groSe Werte der Aktivierungsenergie, die aus der Auftragung dcr Leitf&higlteit fiber der Temperatur berechnet werden, weisen darauf hin, da13 die Leitfahigkcit mit Ionen verkniipft werden kann.
Materials Science and Engineering: B, 2003
Polycrystalline samples of [Pb 0.92 (La 1(z Bi z) 0.08 ][Zr 0.60 Ti 0.40 ] 0.98 O 3 (z 0/0.0, 0.3... more Polycrystalline samples of [Pb 0.92 (La 1(z Bi z) 0.08 ][Zr 0.60 Ti 0.40 ] 0.98 O 3 (z 0/0.0, 0.3, 0.6, 0.9, 1) (PLBZT) were synthesized using a high-temperature solid-state reaction technique. The formation of the PLBZT compounds in a particular crystallographic phase as a function of Bi concentration was checked through X-ray diffraction (XRD). S.E.M. study of PLBZT with higher magnification and resolution shows the uniform distribution of particles/grains on the surface of the samples. Dielectric constant and tangent loss of the samples in wide temperature and frequency range provided the nature of phase transition. The diffuse phase transition was observed for higher z. An increase in permittivity maxima temperature (i.e. the transition temperature) was also observed with increasing Bi concentration. The values of resistivity of all the samples are very high (10 9 V-cm).
Journal of Materials Science, 2004
Detailed studies of structural, dielectric, and electrical characteristics of a precursor solutio... more Detailed studies of structural, dielectric, and electrical characteristics of a precursor solution method synthesized, bismuth and lead titanate modified manganese titanate (MnTiO 3) are reported in this communication. Analysis of X-ray diffraction data shows that MnTiO 3 goes through a structural change on the addition of Bi and PbTiO 3 (PT). At room temperature, MnTiO 3 has a rhombohedral crystal system, which changes to an orthorhombic crystal system with the addition of bismuth in it (i.e., BiMn 1/2 Ti 1/2 O 3 = BMT). On further addition of PT in BMT (i.e., 0.5 BiMn 1/2 Ti 1/2 O 3-0.5PbTiO 3), a stable perovskite structure with tetragonal symmetry was obtained. It is found that the addition of bismuth and lead titanate effectively reduces the grain size, and hence enhances the relative permittivity of the compound. It is further found that ferroelectricity can be induced in a non-ferroelectric MnTiO 3 on the addition of Bi and PbTiO 3 in it. However, the addition of bismuth and lead titanate increases the leakage current density of the compound.
Journal of Materials Science, 2004