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

The synthesis of BaSn(OH)(6) acicular crystals by precipitation at 100 degreesC from aqueous solutions and their transformation in the perovskitelike compound BaSnO3 was investigated. Single acicular crystals 100-200 mum in length were obtained from a 0.05 M solution, whereas bundlelike aggregates of 20-40 mum 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 Angstrom, b = 6.340 +/- 0.001 Angstrom, c = 10.563 +/- 0.001 Angstrom, beta = 128.51 +/- 0.01degrees, alpha = gamma = 90degrees. The BaSn(OH)(6) particles decomposed to BaSnO3 and water at approximately 270 degreesC and the original morphology was retained. The resulting product had specific surface area up to 30-40 m(2)/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 degreesC 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 degreesC.