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Frequency-dependent dielectric characteristics of ferroelectric $SrBi_2Nb_2O_9$ ceramics

Venkataraman, Harihara B and Varma, KBR (2004) Frequency-dependent dielectric characteristics of ferroelectric $SrBi_2Nb_2O_9$ ceramics. In: Solid State Ionics, 167 (1-2). pp. 197-202.

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Abstract

The dielectric properties of ferroelectric $SrBi_2Nb_2O_9$ (SBN) ceramics have been studied in the frequency range of 100 Hz to 1 MHz at various temperatures (300–823 K). A strong low frequency dielectric dispersion (LFDD) is encountered in these ceramics in the 573–823 K temperature range. Electrical conductivity data indicate that the conductivity in SBN is essentially due to oxygen vacancies and the activation energy for the conduction in the high temperature region is found to be 0.90 eV. The dielectric constants measured as a function of frequency (100 Hz–1 MHz) in the 300–823 K temperature range have been found to fit to the Jonscher’s dielectric dispersion relations: $\varepsilon_r' = \varepsilon_\infty+ sin(n(T)\pi/2)\omega^{n(T) - 1}a(T)/\varepsilon_o$ and $\varepsilon_r" = \sigma/\varepsilon_o\omega+ cos(n(T)\pi/2)\omega^{n(T)-1}a(T)/\varepsilon_o.$ The high frequency (1 MHz) dielectric constant $(\varepsilon_\infty)$ shows a peak at $T_c$ (723 K).The coefficient A(T) (=a(T)S/L) and the exponent n(T) of the Jonscher’s expression are determined. The exponent n(T) is found to be minimum at the Curie temperature, $T_c.$ The parameter A(T), which indicates the strength of the polarizability, shows a prominent peak in the vicinity of the Curie temperature.

Item Type: Journal Article
Additional Information: The copyright belongs to Elsevier.
Keywords: Strontium bismuth niobate;Ferroelectric;Low frequency dielectric dispersion;Universal dielectric response
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 27 May 2006
Last Modified: 19 Sep 2010 04:27
URI: http://eprints.iisc.ernet.in/id/eprint/6826

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