Phase Equilibria in the TiO ₂ ‐Rich Region of the System BaO‐TiO ₂

Abstract

Phase relations in the system BaO‐TiO 2 from 67 to 100 mol% TiO 2 were investigated at 1200° to 1450°C in O 2 . Data were obtained by microstructural, X‐ray, and thermal analyses. The existence of the stable compounds Ba 6 Ti 17 O 40 , Ba 4 Ti 13 O 30 , BaTi 4 O 9 , and Ba 2 Ti 9 O 20 was confirmed. The compound BaTi 2 O 5 is unstable and either forms as a reaction intermediate below the solidus or crystallizes from the melt. The compounds Ba 6 Ti 17 O 40 and Ba 4 Ti 13 O 30 decompose in peritectic reactions, and BaTiO 3 and Ba 6 Ti 17 O 40 react to form a eutectic. Special conditions are required for the formation of Ba 2 Ti 9 O 20 , which decomposes in a peritectoid reaction at 1420°C. The new phase diagram is presented.