Thin-film solid-state reactions of solid BaCO 3 and BaO vapor with (1 0 0) rutile substrates

Abstract

Thin-film solid-state reactions in the BaCO 3–TiO 2 and BaO–TiO 2 systems have been experimentally studied in air and in vacuum, respectively, on (1 0 0) TiO 2 substrates. The solid–solid reactions in vacuum and in air showed that different processes occur during BaTiO 3 formation: an intermediate Ba 2TiO 4 compound is always observed in vacuum but not in air. The crystallographic orientations between the reaction products and the TiO 2 substrate were investigated by X-ray diffractometry and transmission electron microscopy. One orientation relationship has been found for BaTiO 3 after a solid–solid reaction, whereas different orientation relationships for BaTiO 3 have been identified after a vapor–solid reaction. At high temperatures, Ti-rich polytitanates were grown in both types of solid-state reactions but with quite different textures. The crystallographic relationships and their origins are analyzed.