Mechanism of the Formation of Ba_2Ti_9O_(20)-Based Phases in the Course of Solid-Phase Interaction in the BaO-TiO_2(ZrO_2) and Cs_2O-BaO-TiO_2 (ZrO_2) Systems

摘要

The mechanism of solid-phase interaction in the BaO-TiO_2 (ZrO_2) and Cs_2O-BaO-TiO_2 (ZrO_2) system is investigated. It is established that the formation of the Ba_2Ti_9O_(20) compound and Ba_2Ti_9O_(20)-based solid solutions is a multistage process proceeding through the formation of intermediate pahses. The solid-phase interaction in the BaO-TiO_2 (ZrO_2) system occurs throuh the formation of the BaTi_4O_9 intermediate compound. The Ba_2Ti_9O_(20) single-pahse product is formed only in the presence of ZrO_2 (0.82 mol%) upon heat treatment at a temperature of 1250 deg C for 5h. In the Cs_2O-BaO-TiO_2 (ZrO_2) system, the BaTi_5O_(11) metastable intermediate phase is formed at the first stage of the solid-phase interaction. The Cs_xBa_(2-x/2)Ti_(9-y)Zr_yO_(20) single-phase solid solutions are prepared upon heat treatment at 1100 deg C for 1h. It is demonstrated that, in the Ba_2Ti_9O_(20) structure, cesium can isomorphously substitute for barium with the formation of Cs_xBa_(2-x/2)Ti_(9-y)Zr_yO_(20) solid solutions (O <= x <= 0.8, y = 0 and 0.09).