СТАННАТ СТРОНЦИЯ

BaSnO₃ crystallizes in a cubic perovskite structure. The lattice constant of BaSnO₃ is a=4.1163 ?.

BaSnO3 with cubic perovskite structure exhibits good dielectric properties. Because of these characteristic properties, BaSnO₃ ceramic is becoming more and more important in material technology. It can be used to prepare thermally stable capacitors and to fabricate ceramic boundary layer capacitors. In recent years, BaSnO₃ has been found to be a very promising sensor material and has therefore received the most attention. In pure as well as doped forms, stannates have been investigated as potential solid-state sensor materials for many gases, including CO, NO_x, H₂ and CO₂. BaSnO₃ has also been used in the preparation of multifunctional temperature–humidity–gas sensors by combining it with BaTiO₃. Detection of gas in BaSnO₃ sensors is achieved by measurement of the electrical properties changes such as resistance and conductivity. The changes are induced in the semiconducting oxide form of BaSnO₃ following adsorption of any given gases on the solid surface. The gas sensitivity of this semiconducting oxide is related to the surface reaction process.

BaSnO₃ powder with a crystallite size of 27.6 nm was prepared through a hydrothermal reaction of a peptized SnO₂·xH₃O and Ba(OH)₃ at 250°C. This was followed by crystallization of this hydrothermal product at 330°C. The peptization of the SnO₃·xH₃O gel is dependent on the pH value. Through peptization, the mean particle size of SnO₃·xH₃O in the aqueous solution has been decreased by a factor of 100 to 8 nm. A limited agglomeration in the sol-prepared powder was observed under the microscope. The structure evolution and crystallization behaviors of the solprepared powders were investigated by TG-DTA, IR and XRD. The BaSn(OH)₆ phase in the as-prepared powder transforms into an amorphous phase at 260°C, from which the BaSnO₃ particles nucleate and grow with an increase in temperature. The single-phase BaSnO₃ powder has been obtained at a temperature as low as 330°C. This sol-prepared powder is more sinterable than the gel-prepared powder and can be sintered to a ceramic at 340°C with 90.7% of the theoretic density.