Patri Tirupathi; Anil Tejomurthula; Nawnit Kumar; Mukul Pastor; R. N. P. Choudhary
Abstract
The polycrystalline sample of Sr-modified Pb(Zr0.5Ti0.5)O3 (i.e. Pb1-xSrx(Zr0.5Ti0.5)O3 (x = 0.05-0.15)) ceramics were synthesized (close to morph-tropic phase boundary) by a cost effective (solid state reaction) method. Detailed investigation of structural phase transition was carried out using room ...
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The polycrystalline sample of Sr-modified Pb(Zr0.5Ti0.5)O3 (i.e. Pb1-xSrx(Zr0.5Ti0.5)O3 (x = 0.05-0.15)) ceramics were synthesized (close to morph-tropic phase boundary) by a cost effective (solid state reaction) method. Detailed investigation of structural phase transition was carried out using room temperature X-ray diffraction data adopting Rietveld refinement technique. The coexistence of two crystal phases (i.e., tetragonal (P4mm) and rhombohedral (R3c) for x = 0.05, and single tetragonal (P4mm) phase for x = 0.1, 0.15) were observed. Elemental analysis, grain shape and size distribution were studied using scanning electron microscope. The decrease in grain size on increasing Sr 2+ concentration was also observed. Detailed analysis of temperature and frequency dependence of dielectric exhibits the increase in dielectric permittivity as function of Sr 2+ concentration at room temperature. Beside this, the greatly reduced Curie (TC) temperature and broadening of dielectric maxima as function of increasing Sr 2+ concentration in PZT was observed. The multiple relaxation processes associated with grain, grain boundaries and interfacial polarization was noted for x=0.05 and x=0.10 to analyze the Nyquist plots. The dominant of grain boundary resistance with increasing in dopent concentration x=0.15 was observed.
Nawnit Kumar; Patri Tirupathi; Bineet Kumar; Mukul Pastor; A. C. Pandey; R. N. P. Choudhary
Abstract
We reports structural, microstructural and dielectric characteristics of Sr 2+ doped PZT (50/50) ceramic. X-ray diffraction reveals that the system exhibit coexistence of two phases (Tetragonal and rhombohedral) at room temperature. Typical relaxor behavior was observed by the dielectric studies and ...
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We reports structural, microstructural and dielectric characteristics of Sr 2+ doped PZT (50/50) ceramic. X-ray diffraction reveals that the system exhibit coexistence of two phases (Tetragonal and rhombohedral) at room temperature. Typical relaxor behavior was observed by the dielectric studies and confirmed by Vogul-Fulcher fitting. The observed relaxor was predicted as existence of nanopolar regions due to short range ordering in presence of oxygen vacancies. The evidence for oxygen vacancies was studied by conductivity and polarization studies. Moreover, at 270 °C one more phase transition is noted which was ascribed to structural phase transition. Present study has scientific significance to distinguish the performance of oxygen vacancies in ferroelectric materials.
B. C. Sutar; Piyush R. Das; R. N. P. Choudhary
Abstract
Lead-free polycrystalline material Sr(Bi0.5V0.5)O3 was prepared using a high- temperature solid state reaction technique (calcinations and sintering temperature =850 and 950 o C, respectively) using high-purity ingredients. The formation of the material in the monoclinic crystal structure was confirmed ...
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Lead-free polycrystalline material Sr(Bi0.5V0.5)O3 was prepared using a high- temperature solid state reaction technique (calcinations and sintering temperature =850 and 950 o C, respectively) using high-purity ingredients. The formation of the material in the monoclinic crystal structure was confirmed by preliminary X-ray structural analysis with room temperature data.The nature of microstructure obtained by scanning electron microscopy (SEM) shows that the compound has well defined grains which are uniformly distributed throughout the surface of the sample. Detailed studies of dielectric and impedance properties of the material carried out in the frequency range of 1 kHz –1MHz at different temperatures (30 0 C to 455 0 C) have provided many interesting properties. Detailed studies of dielectric properties of the compound showed an existence of diffus e phase transition around 258 0 C. The temperature dependence of electrical parameters (impedance, modulus etc.) of the material exhibits a strong correlation of its microstructure with the electrical parameters. The negative temperature coefficient of resistance (NTCR) behavior also was observed in the material. The complex electric modulus analysis indicates the presence of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The nature of variation of dc conductivity with temperature confirms the Arrhenius behavior of the material. The ac conductivity spectra show a typical signature of an ionic conducting system, and are found to obey Jonscher’s universal power law.
Anita Mekap; Piyush R. Das; R. N. P. Choudhary
Abstract
The polycrystalline sample of ZnSb2O4 was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction (XRD) studies of powder sample of ZnSb2O4 showed the formation of single-phase compound at room temperature. The surface morphology of the pellet sample of ZnSb2O4 was ...
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The polycrystalline sample of ZnSb2O4 was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction (XRD) studies of powder sample of ZnSb2O4 showed the formation of single-phase compound at room temperature. The surface morphology of the pellet sample of ZnSb2O4 was recorded at room temperature using a scanning electron microscope (SEM). Detailed studies of dielectric properties (εr, tan δ) and impedance parameters of the material provide an insight into the electrical properties and understanding of types of relaxation process occurred in the material. Temperature variation of dc conductivity shows that this compound exhibits negative temperature coefficient of resistance (NTCR) and frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law.
P. S. Sahoo; B. B. Mohanty; R. N. P. Choudhary
Abstract
The advent of nanoscience & technology have completely changed the orientation/direction of studies of eco-friendly (lead-free) materials bringing them at the forefront of scientific developments with considerably enhanced physical properties suitable for a wide variety of challenging applications. ...
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The advent of nanoscience & technology have completely changed the orientation/direction of studies of eco-friendly (lead-free) materials bringing them at the forefront of scientific developments with considerably enhanced physical properties suitable for a wide variety of challenging applications. Barium based ferroelectric materials have gained much importance due to their vast applications as they possess high dielectric constant, non-linear spontaneous polarization, negative temperature coefficient of resistance behavior etc.. All these characteristics stimulated the researchers to replace toxic and hazardous lead based materials by barium based TB materials from industry. Our present research work deals with the synthesis of polycrystalline samples of Ba2Sr3RTi3V7O30 (R = Gd, Sm) by a high temperature solid state reaction technique and a comparative study of the electrical properties of the samples. Preliminary structural (XRD) analyses of these compounds show the formation of single-phase orthorhombic structures at room temperature having average crystallite size of the order of some nanometer for both the compounds. The electrical properties for both the samples are studied in a wide range of temperature (30–500 o C) and frequency (100Hz-1MHz). The dielectric properties suggest that both the compounds have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 230 and 313 0 C for R= Sm and Gd respectively at frequency 100 kHz).The bulk resistance of the materials exhibits negative temperature coefficient of resistance behavior as observed in semiconductors.
Jeewan Kumar; S. N. Choudhary; K. Prasad; R. N. P. Choudhary
Abstract
The polycrystalline sample of 0.25Ba(Bi1/2Ta1/2)O3-0.75BaTiO3 was synthesized using conventional solid state reaction technique. XRD analysis indicated the formation of a single-phase orthorhombic structure. The SEM analysis shows the grain sizes to be 0.12 to mm. Complex electric modulus analyses suggested ...
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The polycrystalline sample of 0.25Ba(Bi1/2Ta1/2)O3-0.75BaTiO3 was synthesized using conventional solid state reaction technique. XRD analysis indicated the formation of a single-phase orthorhombic structure. The SEM analysis shows the grain sizes to be 0.12 to mm. Complex electric modulus analyses suggested the dielectric relaxation to be of non-Debye type. Dielectric studies indicated the relaxor behavior of 0.25Ba(Bi1/2Ta1/2)O3-0.75BaTiO3. The correlated barrier hopping model was employed to explain the mechanism of charge transport in the system. The ac conductivity is found to obey the Jonscher’s power law. The nature of variation of dc conductivity with temperature suggested NTCR behavior with activation energy 0.36eV. The studied material can be a potential candidate for capacitor applications.
Subhadarsani Sahoo; Dhiren K. Pradhan; R. N. P. Choudhary; B. K. Mathur
Abstract
The polycrystalline sample of (K0.5Bi0.5)(Fe0.5Nb0.5)O3 was synthesized by a high- temperature solid-state reaction technique. The material crystallizes in cubic structure at room temperature. The dielectric properties of the material were investigated in a temperature range from 30-200 ºC in the ...
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The polycrystalline sample of (K0.5Bi0.5)(Fe0.5Nb0.5)O3 was synthesized by a high- temperature solid-state reaction technique. The material crystallizes in cubic structure at room temperature. The dielectric properties of the material were investigated in a temperature range from 30-200 ºC in the frequency range (102–107 Hz). Impedance data is well fitted using proper equivalent circuit composed of a parallel resistance and capacitance in series with a parallel resistance, constant phase element and a capacitance. The compound shows a typical negative temperature coefficient of resistance type (NTCR) behavior like that of semiconductors. Modulus spectroscopy and dielectric conductivity formalism were employed to study dielectric relaxation phenomena in the material. The frequency dependence of conductivity is well fitted to Jonscher’s single power law.