# Frequency Dependent Dielectric Characteristics of Undoped and Vanadium-Doped $SrBi_{2}Nb_{2}O_{9}$ Ferroelectric Ceramics: A Comparative Study

Venkataraman, Harihara B and Varma, KBR (2005) Frequency Dependent Dielectric Characteristics of Undoped and Vanadium-Doped $SrBi_{2}Nb_{2}O_{9}$ Ferroelectric Ceramics: A Comparative Study. In: Ferroelectrics, 324 . pp. 121-132.

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## Abstract

The dielectric properties of undoped and vanadium (10 mol%) doped $SrBi_{2}Nb_{2}O_{9}$ ferroelectric ceramics were studied in the 100 Hz to 1 MHz frequency range at various temperatures (300-823 K). The dielectric constants of vanadium doped ceramics were higher than those of undoped ceramics. A strong low frequency dielectric dispersion (LFDD) was encountered in these ceramics in the 573-823 K temperature range. The dispersion was stronger at low frequencies and higher temperatures for vanadium - doped ceramics. The dielectric constants measured in the wide frequency and temperature ranges for both the samples were found to fit well to the Jonscher's dielectric dispersion relations: $\epsilon_{r}^{'} = \epsilon_{\infinity} + sin (n(T)\pi /2) \omega^{n(T)-1} a(T)/\epsilon_{o} and \epsilon_{r}^{''} = \sigma/\epsilon_{o} \omega + cos (n (T) \pi /2) \omega^{(n(T)-1} a(T)/\epsilon_{o}$. The lattice dielectric constant $(\epsilon_{\infinity})$ shows a peak at $T_{c}$. The coefficient A(T)(= a(T)S/L) and the exponent n (T) of the Jonscher's expression were determined. The exponent n (T) was found to be minimum at the Curie temperature, $T_{c}$ . The value of n for the vanadium-doped samples was less than that of the undoped one. The parameter A(T), which indicates the polarizing power, showed a prominent peak in the vicinity of the Curie temperature for both the samples. However, the value of A for the vanadium-doped samples was higher than that of undoped SBN ceramics.

Item Type: Journal Article Copyright for this article belongs to Taylor and Francis Ltd. Layered perovskites, strontium bismuth niobate, Ac conductivity; frequency dependence; universal dynamic response Division of Chemical Sciences > Materials Research Centre 19 Jan 2006 27 Aug 2008 11:41 http://eprints.iisc.ernet.in/id/eprint/5160