Synthesis of nanosized BaSnO3 powders

Abstract

The metal alkoxide route for preparing nanocrystalline BaSnO3 powders has been developed for the first time. Derived from the synthesized bimetal alkoxide precursor BaSn(OPri)6, BaSnO3 with a particle size of 20 to 60 nm has been obtained. Due to the high phase transformation temperature (above 550°C) the particles are strongly agglomerated and the specific surface area of the powder is only 17.0 m²/g. Therefore, a hydrothermal synthesis technique for preparing nanosize BaSnO3 powders with a higher surface area and a lower aggregation degree has been developed. The reactivity of the SnO2.xH2O precursor in this technique is found to be dependent on the pH value. The influence of the concentration of Ba(OH)2, the Ba:Sn ratio, the temperature and duration of hydrothermal reaction and the solvent on the properties and the structure of the resulting powder has been studied. To minimize the agglomeration and aggregation, the precursor SnO2.xH2O is peptized with ammonia and modified with Genapol X-080, respectively. The SnO2.xH2O precursor becomes narrowly dispersed with a particle size of ca. 8 nm via peptization. Through modification the specific surface area of the obtained BaSnO3 has been increased to over 50 m²/g by optimizing the concentration of the surfactant. The BaSnO3 powder with a maximal specific surface of 57.0 m²/g has been obtained by combination of modification and peptization thanks to the limitation of agglomeration and the decreased particle size (10 to 30 nm). A densified ceramic tape has been fabricated at 1500°C through redispersing BaSnO3 with TEA and thereafter tape casting. The solid solution region of BaSbxSn1-xO3 exists for 0 ≤ x < 0.12. The conductivity of BaSnO3 is improved by doping 10 at.% Sb5+.