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Behera S.,Hi Technology College Engineering | Das P.R.,Siksha O' Anusandhan University | Nayak P.,Sambalpur University | Padhee R.,Siksha O' Anusandhan University
Advanced Science Letters | Year: 2014

Complex modulus analysis of new rare earth-based tungsten-bronze ceramic oxides, Na2Pb2R2W2Ti4Ta4O30 (R = La, Y), prepared by high-temperature solid-state reaction technique have been carried out. The complex electric modulus analyses indicate the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. Appearance of peaks in the plot of imaginary part of modulus with frequency at a fixed temperature, suggest the relaxation process in the materials. The shift in peak towards high frequency side with rise in temperature suggests increase in rate of relaxation with increase in temperature. The temperature variation of relaxation time obeys Arrhenius law. The frequency dependence of electric modulus and impedance of the materials show the presence of non-Debye type of relaxation. Temperature dependence of dc conductivity confirm negative temperature coefficient of resistance behavior of the materials. © 2014 American Scientific Publishers All rights reserved. Source


Behera S.,Hi Technology College Engineering | Parida B.N.,Institute of Physics, Bhubaneswar | Nayak P.,Sambalpur University | Das P.R.,Institute of Physics, Bhubaneswar
Journal of Materials Science: Materials in Electronics | Year: 2013

A new complex oxide (Na2Pb2Pr2W 2Ti4Ta4O30) of tungsten bronze structural family has been synthesized by a high-temperature solid-state reaction (mixed-oxide) route at 1,050 C. Room temperature structural analysis shows the formation of a single phase new compound. Study of microstructure of the pellet sample, recorded by scanning electron microscope, exhibits the uniform distribution of different size and shape of grains (with a few small voids) on the surface of the sample. Detailed studies of dielectric properties as a function of frequency and temperature show a dielectric anomaly above room temperature suggesting the existence of a ferroelectric phase transition in the material. Impedance spectroscopic analysis and electrical conductivity of the material exhibit a strong correlation between microstructure and electrical parameters. The temperature dependence of dc conductivity of the compound follows Arrhenius equation. The frequency and temperature dependence of ac conductivity (with fittings) shows the signature of Jonscher's universal power law. The existence of non-exponential-type of conductivity relaxation in the compound was confirmed. © 2012 Springer Science+Business Media, LLC. Source


Parida B.N.,Siksha O' Anusandhan University | Das P.R.,Siksha O' Anusandhan University | Padhee R.,Siksha O' Anusandhan University | Behera S.,Hi Technology College Engineering | Choudhary R.N.P.,Siksha O' Anusandhan University
Journal of Materials Science: Materials in Electronics | Year: 2014

The polycrystalline sample of Li2Pb2Nd 2W2Ti4Ta4O30 was prepared by a solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. Detailed studies of the nature of variation of dielectric constant, tangent loss and polarization with temperature and frequency confirmed the existence of ferroelectricity in the material. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its micro-structure (i.e., bulk, grain boundary, etc.). The nature of variation of pyroelectric-coefficient and current with temperature suggests that material has good pyroelectric properties useful for pyroelectric detector. © 2014 Springer Science+Business Media New York. Source


Das P.R.,Institute of Physics, Bhubaneswar | Behera S.,Hi Technology College Engineering | Padhee R.,Institute of Physics, Bhubaneswar | Nayak P.,Sambalpur University | Choudhary R.N.P.,Institute of Physics, Bhubaneswar
Journal of Advanced Ceramics | Year: 2012

The polycrystalline sample of complex tungsten-bronze type compound (Na2Pb2La2W2Ti4Ta4O30) was prepared by a high-temperature solid-state reaction technique. Room temperature preliminary structural study using X-ray diffraction (XRD) data exhibits the formation of a single-phase new compound. The SEM micrograph of the compound exhibits non uniform rectangular grains distributed throughout the sample surface. Detailed studies of dielectric parameters (ɛr, tan δ) as a function of temperature and frequency, and P-E hysteresis (spontaneous polarization) confirmed the existence of ferroelectricity in the material. Complex impedance spectroscopy analysis, carried out as a function of frequency at different temperatures, established a correlation between the microstructure and electrical properties of the material. The electrical relaxation process occurring in the material is temperature dependent. The activation energy found from the Arrhenius plot that the conduction process in the material is of mixed type. The nature of frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law. © 2012, The Author(s). Source


Das P.R.,Siksha O' Anusandhan University | Behera S.,Hi Technology College Engineering | Nayak P.,Sambalpur University
AIP Conference Proceedings | Year: 2011

A new tungsten bronze ceramic sample Na2Pb2Nd 2W2Ti4Ta4O30 was prepared by a high-temperature solid-state reaction technique. X-ray diffraction studies of the compound showed the formation of single-phase orthorhombic crystal structure at room temperature. Surface morphology of the compound was studied by scanning electron microscope (SEM). Study of dielectric properties (εr, tanδ) of the compound at different frequencies (1, 10, 100 kHz and 1 MHz) in a wide temperature range (300-700 K) shows ferroelectric phase transition of diffused type at 400K. © 2011 American Institute of Physics. Source

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