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# Grain Boundary Layer Ceramic Capacitors Based on Donor-doped $Ba(Ti_{1-x}Sn_x)O_3$

Vivekanandan, R and Kutty, TRN (1990) Grain Boundary Layer Ceramic Capacitors Based on Donor-doped $Ba(Ti_{1-x}Sn_x)O_3$. In: Materials Science and Engineering B, 6 (4). pp. 221-231.

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## Abstract

Grain boundary layer capacitors are processed from $Ba(Ti_{1-x}Sn_x)O_3$ solid solutions (0 < x < 0.25), doped simultaneously with donor and acceptor impurities. The starting powders are prepared by the hydrothermal method. Dielectric properties of these ceramics are strongly dependent on the concentration of donor as well as acceptor dopants, the ceramic microstructure and phase contents. It is found that the $3d^n$ configuration of acceptor impurities also influences the dielectric properties. Fine-grained (less than or equal to $3 \mu m$) ceramics show low loss (less than 5%), low $\varepsilon_r$ $(6\times 10^3)$ and high resistivity (greater than or equal to $2.6\times 10^6 \Omega \hspace{2mm} cm$), whereas, the coarse-grained (greater than $25 \mu m$) ceramics show high loss (greater than 100%), high $\varepsilon_r$ $(8.5 \times 10^6)$ and low resistivity (less than or equal to $3 \times 10^4 \Omega \hspace{2mm}cm$). Energy-dispersive X-ray analysis shows uniform distribution of donor and acceptor impurities in these ceramics. Phase content analysis by electron paramagnetic resonance reveals partial coexistence of ferroelectric orthorhombic and tetragonal phases along with the paraelectric cubic phase which directly convert to the rhombohedral phase. Current-voltage characteristics and the frequency effect on dielectric properties are also investigated. The insulting behaviour of the grain boundary layers is explained on the basis of the higher concentration of barium vacancies in these layers and the vibronic activation of the acceptor states in various symmetry configurations of a lattice that undergoes diffuse phase transitions.

Item Type: Journal Article Materials Science and Engineering B Elsevier Copyright of this article belongs to Elsevier. Division of Chemical Sciences > Materials Research Centre 30 Jul 2007 19 Sep 2010 04:38 http://eprints.iisc.ac.in/id/eprint/11575

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