TITLE:
Dielectric Relaxation in Pure Columbite Phase of SrNb2O6 Ceramic Material: Impedance Analysis
AUTHORS:
Karuna Nidhan Singh, Parmendra Kumar Bajpai
KEYWORDS:
Electro Ceramics, Dielectrics, Microstructure, Sintering Optimization, Dielectric Relaxation
JOURNAL NAME:
World Journal of Condensed Matter Physics,
Vol.1 No.2,
May
6,
2011
ABSTRACT: Controlling the heating rate during calcination and cooling rate during sintering, pure columbite like phase of SrNb2O6 is synthesized. By optimizing the sintering temperature, ceramic with density (>92%) is achieved for material calcined at 11250C and sintered at 12000C. The ceramic shows orthorhombic structure with lattice parameters a = 11.011 Å b = 7.7136 Å, c = 5.5969Å having average grain size ≈ 1.03 μm. The temperature dependent dielectric response shows a peak at temperature 300.90C, which shows significant dielectric dispersion towards high temperature side of the peak with almost dispersion free low temperature side; an effect observed in relaxors. Dielectric dispersion in the material is fitted with the Jonscher’s relation. Impedance analysis suggests strongly temperature dependent relaxation. The dielectric relaxation is polydispersive and conduction is mainly through grains. The equivalent circuit model for the impedance response is proposed and the temperature dependence of circuit elements deduced. The frequency dependent ac conductivity at different temperatures indicated that the conduction is governed through thermally activated processes. AC conduction activation energies are estimated from Arrhenius plots and conduction mechanism is discussed.