Investigations on the liquid phase in barium titanate ceramics with silicaadditives

Additives Of SiO2 lower the sintering temperature of BaTiO3 ceramics and pr omote anomalous grain growth. However, the nature of the working liquid pha se is not clear. A binary eutectic is out of the question because the syste m BaTiO3-SiO2 is not a binary one, as shown by Robbins [Robbins, C. R., Syn thesis and growth of fresnoite (Ba2TiSi2O8) from a TiO2 flux and its relati on to the system BaTiO3-SiO2. Journal of Research of the National Buereau o f Standards - A. Physics and Chemistry, 1970, 74A, 229-232]. Guha and Kolar [Guha, J. P. and Kolar, D., Phase equilibria, sintering characteristics an d dielectric properties in the BaTiO3-rich portion of the system BaO-TiO2-S iO2. In 5th Conference on Ceramics for Electronics, Liblice, 1974, pp. 1-9] found a ternary eutectic with a composition of 33 mol% BaO, 54 mol% TiO2 a nd 13 mol% SiO2. We examined powder tips of this composition and ones of pu re SiO2 in contact with BaTiO3 green bodies by heating microscopy. The resu lts suggest that the ternary eutectic develops in sintering bodies with SiO 2 addition. During further sintering the composition of the liquid phase is changed and this modified melt is able to trigger anomalous grain growth. (C) 2001 Elsevier Science Ltd. All rights reserved.