Water vapor-assisted solid-state reaction for the synthesis of nanocrystalline BaZrO₃ powder

Abstract

Solid-state reaction between BaCO₃ and ZrO₂ is the simplest method to prepare BaZrO₃, which is an important refractory structural material with a very high melting point and a low chemical reactivity. However, since the solid-state formation of the BaZrO₃ phase requires high calcination temperature, this method typically produces larger particles unsuitable for the sintering process than the solution methods. In this study, we investigated the reaction behavior between very fine ZrO₂ (70 nm) and coarse BaCO₃ (1.5–5.7 µm) and described the water vapor-assisted solid-state synthesis of BaZrO₃. Nanocrystalline BaZrO₃ powder (~80 nm) was obtained by solid-state reaction at 1050°C in air. The BaZrO₃ formation was accelerated by water vapor-assisted reaction. The apparent activation energy for the formation reaction was calculated to be 323 ± 21 kJ/mol and 263 ± 46 kJ/mol in air and humid air with H₂O of 0.5 atm, respectively. In the 1 atm water vapor atmosphere, almost single-phase BaZrO₃ was obtained by calcination at 750°C.