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Effect of charge redistribution through secondary phase formation on PTCR characteristics of $n-BaTiO_3$ ceramics

Kutty, TRN and Hari, NS (1998) Effect of charge redistribution through secondary phase formation on PTCR characteristics of $n-BaTiO_3$ ceramics. In: Materials Letters, 34 (1-2). pp. 43-49.

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Abstract

Heterogeneous addition of alumina, up to 10 mol%, as a grain boundary modifier in $nBaTi0_3$ PTCR ceramics modifies the p-T characteristics whereby $T_{max}$ is shifted from 455 to 700 K, accompanied by the decrease in $p_{max}$. Whereas $B_2O_3$ shifts the $T_{max}$ to 410 K with little change in $p_{max}$. The grain boundary segregation of alumina leads to the formation of secondary phases, $BaAl_6TiO_{12 }$ and $Ba_3Al_{10}TiO_{20}$. The changing pattern of trap states is evident from the presence of $Ti^{4+}-O^--Al^{3+}$ type hole centers at the grain boundary layer regions, as identified by the EPR spectra. The charge redistribution among the inter-band gap defect states across the Curie temperature is substantiated by the EPR results.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to elsevier.
Keywords: Grain boundary modifiers;Secondary phases;PTCR;BaTiO3 ceramics;Charge trapping
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 04 Jan 2007
Last Modified: 19 Sep 2010 04:33
URI: http://eprints.iisc.ernet.in/id/eprint/9224

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