Recrystallization of fine-crystalline barium titanate in low-density water medium

• BaTiO 3 recrystallization occurred in subcritical vapor or supercritical water. • Reversible interaction of BaTiO 3 with H 2 O enhanced its solid-phase mobility. • BaTiO 3 recrystallization changed its crystal shape and dispersion composition. • BaTiO 3 recrystallization was accompanied with increase in tetragonality. Fine-crystalline barium titanate was synthesized from a mixture of barium hydroxide monohydrate and titanium dioxide in water vapor medium at 200 °C and 1.55 MPa and subsequently treated in subcritical vapor and supercritical water at 200−400 °C and 1.55-26.3 MPa. Recrystallization of synthesized powder led to an increase in average crystal size and to tetragonal distortion of BaTiO 3 structure. Formation of highly tetragonal BaTiO 3 was observed after the treatment in supercritical water at 400 °C, 26.3 MPa. Treatment of BaTiO 3 crystals in water vapor and supercritical water made for elimination of structural defects and for changes in the morphology and dispersion composition of the powder. The results are of importance for effective production of barium titanate powder of different dispersion as raw material for ferroelectric ceramics.