Synthesis of Tin Oxide (SnO<sub>2</sub>) by Precipitation

Abstract

Aqueous solutions of tin (II) chloride dihydrate and oxalic acid dihydrate were prepared and mixed using two protocols: (1) fixed former concentration and variable latter concentrations and (2) fixed latter concentration and variable former concentrations. Following filtering, washing, and drying, the precipitates were calcined and ground. The calcined powders were characterised in terms of mineralogy and the particle size and morphology of the resultant tin oxide particles and agglomerates. The morphologies of the uncalcined tin oxalate also were examined. In nine of the ten samples, the tin oxalate precipitates consisted of prismatic elongated crystals. In the remaining sample, the low concentrations of solutions probably resulted in the crystallisation of smaller equiaxed particles. Regardless of the particle size or shape of the tin oxalate, the resultant particle size of the tin oxide was ~75 nm and the morphology was consistently spherical. The consistent particle size is attributed to the low solution concentrations used. The tin oxide particles were heavily agglomerated into plates of ~0.5 μm diameter. This morphology probably resulted from the plastic deformation during grinding of the calcined tin oxide, which was likely to have been subject to surface water adsorption on the fine particles. Under the experimental conditions investigated, there were no particle or agglomerate size dependencies on the solution concentrations and mixing method.