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Hydrothermal synthesis of Ba(Ti, Sn)O3 fine powders and dielectric properties of the corresponding ceramics

Vivekanandan, R and Kutty, TRN (1988) Hydrothermal synthesis of Ba(Ti, Sn)O3 fine powders and dielectric properties of the corresponding ceramics. In: Ceramics International, 14 (4). pp. 207-216.

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Fine powders of submicron-sized crystallites of BaTiO3 were prepared at 85–130°C by the hydrothermal method, starting from TiO2.ξH2O gel and Ba(OH)2 solution. The products obtained below 110°C incorporated considerable amounts of H2O and OH− in the lattice. As-prepared BaTiO3 is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH− ions. Hydrothermal reaction of SnO2.ξH2O gel with Ba(OH)2 at 150–260°C gives rise to the hydrated phase, BaSn(OH)6.3H2O, due to the amphoteric nature of SnO2.ξH2O which stabilises Sn(OH)62− anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH)6.3H2O converts to BaSnO3 through an intermediate, BaSnO(OH)4. Solid solutions of Ba(Ti,Sn)O3 are directly formed from (TiO2 + SnO2)..ξH2O gel up to 35 mol% SnO2. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH)6.3H2O and BaTiO3, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O3. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O3 ceramics are explained on the basis of the prevailing diffuse phase transition behaviour.

Item Type: Journal Article
Publication: Ceramics International
Publisher: Elsevier
Additional Information: Copyright of this article belongs to Elsevier Science.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 12 Aug 2009 10:24
Last Modified: 19 Sep 2010 05:39
URI: http://eprints.iisc.ac.in/id/eprint/21803

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