Synthesis and characterization of BaSn(OH)₆ and BaSnO₃ acicular particles

The synthesis of BaSn(OH)₆ acicular crystals by precipitation at 100 °C from aqueous solutions and their transformation in the perovskitelike compound BaSnO₃ was investigated. Single acicular crystals 100–200 μm in length were obtained from a 0.05M solution, whereas bundlelike aggregates of 20–40 μm were precipitated from 0.2–0.6 M solutions. The x-ray diffraction pattern of barium hexahydroxostannate was indexed according to monoclinic symmetry with cell parameters a = 11.029 ± 0.002 Å, b = 6.340 ± 0.001 Å, c = 10.563 ± 0.001 Å = 128.51 ± 0.01°, α = γ = 90°. The BaSn(OH)₆ particles decomposed to BaSnO₃ and water at approximately 270 °C and the original morphology was retained. The resulting product had specific surface area up to 30–40 m²/g and consisted of 10–20 nm crystallites. The larger unit cell edge in comparison to the reference value and the continuous weight loss up to 1200 °C indicate that water is not completely released during decomposition and a substantial amount of proton defects (up to 0.4 mol per mole of BaSnO₃) is incorporated in the perovskite lattice as OH⁻ groups. Normal crystallographic properties of BaSnO₃ are restored only after calcination at 1300 °C.