resumo
The effect of nonstoichiometry on the densification of SrTiO(3) ceramics with Sr/Ti ratios from 0.997 to 1.02 was systematically addressed. The kinetics of densification was studied by dilatometric analysis. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for crystallographic and microstructure characterization. Ti excess enhanced matter transport during sintering whereas Sr excess decreased it. The shrinkage rate and average grain size increased with the decrease of Sr/Ti ratio. Close values of the activation energy for the initial densification and the near constant onset temperature for densification Suggest that identical transport mechanisms control the densification of all the compositions. Small excesses of TiO(2) and SrO were mostly incorporated into the perovskite lattice inducing alterations in the defect chemistry of the material and the mass transport during sintering is controlled by Sr vacancies. Very small stoichiometric variations have a strong influence on the sintering kinetics and resulting microstructure of ST ceramics. (C) 2008 Elsevier Ltd. All rights reserved.
palavras-chave
OXYGEN-ION DIFFUSION; BARIUM-TITANATE; GRAIN-GROWTH; DOPED SRTIO3; DIELECTRIC-PROPERTIES; ACTIVATION-ENERGIES; SINGLE-CRYSTAL; MICROSTRUCTURE; BATIO3; TEMPERATURE
categoria
Materials Science
autores
Amaral, L; Senos, AMR; Vilarinho, PM
nossos autores
Ana Maria de Oliveira e Rocha Senos
Colaborador
Paula Maria Lousada Silveirinha Vilarinho
Vice-Diretoragradecimentos
The authors acknowledge financial support from FCT, FEDER and the European Network of Excellence FAME under the contract FP6-500159-1. Ian Reaney is acknowledged for the discussion on TEM results.