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Dielectric Relaxation and Conductivity of Ba(Mg_(1/3)Ta_(2/3))O_3 and Ba(Zn_(1/3)Ta_(2/3))O_3

Journal of Materials Science & Technology 2014年第4期30卷 311-320页

作者： Md.Monwar Hoque Alo Dutta Sanjay Kumar tripurari prasad sinha Department of Physics Jadavpur University Department of Physics Bose Institute

The frequency dependent dielectric properties of barium magnesium tantalate （BMT）, Ba（Mgl/3Ta2/3）03 and barium zinc tantalate （BZT）, Ba（Znl/3Ta2/3）03 synthesized by solid state reaction technique have been investigated at various temperatures by impedance spectroscopy. BMT and BZT possess cubic structure with lattice parameter a = 0.708 and 0.451 nm, respectively. The resonance peaks due to dielectric relaxation processes are observed in the loss tangent of these oxides. The relaxation in the samples is polydispersive in nature. The temperature dependence of dc conductivity, the most probable relaxation frequency （corn） obtained from tanδ vs logo） plots and ωm obtained from imaginary parts of the complex electrical modulus vs Iogω plots follow the Arrhenius behavior. According to these Arrhenius plots the activation energies of BMT and BZT are about 0.54 and 0.40 eV, respectively. Thus the results indicate that samples are semiconducting in nature. The frequency-dependent electrical data are analyzed in the framework of conductivity and electric modulus formalisms. Both these formalisms show qualitative similarities in relaxation time. Our study points that for complex perovskite oxides with general formula A（B＇B＇）03, the dielectric properties significantly depend on the atomic radii of both A and B type cations. BMT and BZT exhibit enhancement in dielectric property compared to their niobate counterparts. They may find several technological applications such as in capacitors, resonators and filters owing to their high dielectric constant and low loss tangent.

关键词： Perovskite oxides Impedance spectroscopy Dielectric properties Electrical conductivity

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Dielectric Relaxation in Complex Perovskite Oxide Sr(Gd0.5Nb0.5)O3

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Materials Sciences and Applications 2012年第6期3卷 369-376页

作者： Pritam Kumar Ajay Kumar Sharma Bhrigunandan prasad Singh tripurari prasad sinha Narendra Kumar Singh Department of Physics Bose Institute Kolkata India University Department of Physics T. M. Bhagalpur University Bhagalpur India University Department of Physics V. K. S. University Ara India

The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) were used to study the structural and microstructural properties of the ceramics, respectively. The XRD patterns of SGN at room temperature show a tetragonal structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (50 Hz to 1 MHz) at room temperature, and as a function of temperature (60°C to 420°C) indicate polydispersive nature of the material. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy ~0.18 eV. The small value of activation energy of the compound (~0.18 eV) can be explained by mixed ionic-polaronic conductivity mechanism. The grain size of the pellet sample was found to be 1.92 μm. The frequency-dependant electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region.

关键词： Dielectrics Perovskite Oxides X-Ray Diffraction Scanning Electron Micrograph

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