Mechanism of the Formation of Ba2Ti9O20-Based Phases in the Course of Solid-Phase Interaction in the BaO–TiO2(ZrO2) and Cs2O–BaO–TiO2(ZrO2) Systems

Abstract

The mechanism of solid-phase interaction in the BaO–TiO2(ZrO2) and Cs2O–BaO–TiO2(ZrO2) systems is investigated. It is established that the formation of the Ba2Ti9O20 compound and Ba2Ti9O20-based solid solutions is a multistage process proceeding through the formation of intermediate phases. The solid-phase interaction in the BaO–TiO2(ZrO2) system occurs through the formation of the BaTi4O9 intermediate compound. The Ba2Ti9O20 single-phase product is formed only in the presence of ZrO2 (0.82 mol %) upon heat treatment at a temperature of 1250°C for 5 h. In the Cs2O–BaO–TiO2(ZrO2) system, the BaTi5O11 metastable intermediate phase is formed at the first stage of the solid-phase interaction. The Cs x Ba2 – x/2Ti9 – yZr y O20 single-phase solid solutions are prepared upon heat treatment at 1100°C for 1 h. It is demonstrated that, in the Ba2Ti9O20 structure, cesium can isomorphously substitute for barium with the formation of Cs x Ba2 – x/2Ti9 – yZr y O20 solid solutions (0 ≤ x ≤ 0.8, y = 0 and 0.09).