Accelerated formation of barium titanate by solid-state reaction in water vapour atmosphere

Barium titanate (BaTiO3) powders were synthesized from commercially available raw materials (BaCO3 and rutile) without particular mechanochemical processing by solid-state reactions in water vapour atmosphere. The formation rate of BaTiO3 was accelerated by water vapour and single phase of BaTiO3 was obtained by calcination at 700 °C for 4 h in water vapour atmosphere, though high temperature (850 °C for 2.5 h) was required by calcinations in air to complete the reaction. The formation kinetics followed the Valensi–Carter equation, which suggested that the reaction proceeded by a diffusion controlled process. The apparent activation energy for the formation of BaTiO3 in air and water vapour atmosphere was estimated to be 361 ± 20 kJ/mol and 142 ± 17 kJ/mol, respectively. Water vapour is considered to enhance thermal decomposition of BaCO3 and formation of BaTiO3 by attacking surface Ti–O–Ti bonds in TiO2, increasing partial pressure of Ba(OH)2, and producing vacancies in the BaTiO3 structure.