Synthesis of hydrous SnO2 and SnO2-coated TiO2 powders by the homogeneous precipitation method and their characterization

Abstract

Hydrous SnO2 and SnO2-coated TiO2 powders were synthesized by the homogeneous precipitation method using urea and the products were characterized by X-ray diffraction, thermogravimetry, differential thermal analysis, scanning electron microscopy and energy- dispersive X-ray microanalysis. Electrical conductivities were measured with an impedance analyser. Hydrous SnO2 powder prepared under conditions without SO42− ions was a bulky product containing 75 wt% of water. The addition of SO42− ions to the solution changed bulky hydrous SnO2 to a dense product; approximately spherical particles were obtained with an average particle size of 0.14 ± 0.03 μm. with 13.5 wt % of absorbed water. Antimony-doped hydrous SnO2 prepared under conditions with SO42− ions consisted of approximately spherical particles with an average particle size of 0.17 ± 0.04 μm with 15.0 wt % of absorbed water. Hydrous SnO2-coated TiO2 powders with a good dispersion state and with various Sn/Ti ratios were prepared under conditions with SO42− ions. All the as-prepared coated powders were white, but the products doped with Sb3+ ions were turned to pale blue by heat treatment at 600° C for 1 h and their electrical conductivities increased by orders of about 3.0 in comparison with those of the other two.