# Extreme values of relative permittivity and dielectric relaxation in $Sr_2SbMnO_6$ ceramics

Majhi, Koushik and Prakash, Shri B and Varma, KBR (2007) Extreme values of relative permittivity and dielectric relaxation in $Sr_2SbMnO_6$ ceramics. In: Journal of Physics D: Applied Physics, 40 . pp. 7128-7235.

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## Abstract

A polycrystalline ceramic of $Sr_2SbMnO_6$ (SSM) was fabricated using the powders obtained by the conventional solid-state reaction route. The dielectric measurements of the ceramic were carried out as a function of frequency (100 Hz–10 MHz) and temperature (190-360 K). SSM exhibited higher relative permittivity $(\sim2 \times 10^5$ for 1 kHz at 360 K) than that for the recently known high permittivity ceramic $CaCu_3Ti_4O_{12}$ (CCTO). It decreased to a relatively low value ($\sim2 \times 10^3$ for 1 kHz) on decreasing the temperature down to 195 K. The modified Cole–Cole equation that included the conductivity term was used to describe the dielectric spectra of the ceramic. Impedance spectroscopy was employed to determine the electrical parameters (resistance, capacitance and relaxation time) of the grain and the grain boundary. The grain and grain boundary conduction and the dielectric relaxation time followed an Arrhenius law associated with activation energies of 0.22 eV, 0.35 eV and 0.24 eV, respectively. Nearly equal activation energies for dielectric relaxation and grain conduction revealed a possibility of invoking a common mechanism to rationalize the permittivity data. The capacitance and resistance associated with the grain boundary were found to be higher than that associated with the grain to a great extent. The incidence of giant relative permittivity and the other experimental findings support the Maxwell–Wagner type of mechanism.

Item Type: Journal Article Copyright of this article belongs to Institute of Physics. Division of Chemical Sciences > Materials Research Centre 17 Dec 2008 14:45 19 Sep 2010 04:52 http://eprints.iisc.ernet.in/id/eprint/16537