Synthesis of Sub-Micron 2SnO·(H2O) Powders Using Chemical Reduction Process and Thermal Calcination

Abstract

Synthesis of sub-micron <TEX>$2SnO{\cdot}(H_2O)$</TEX> powders by chemical reduction process was performed at room temperature as function of viscosity of methanol solution and molecular weight of PVP (polyvinylpyrrolidone). Tin(II) 2-ethylhexanoate and sodium borohydride were used as the tin precursor and the reducing agent, respectively. Simultaneous calcination and sintering processes were additionally performed by heating the <TEX>$2SnO{\cdot}(H_2O)$</TEX> powders. In the synthesis of the <TEX>$2SnO{\cdot}(H_2O)$</TEX> powders, it was possible to control the powder size using different combinations of the methanol solution viscosity and the PVP molecular weight. The molecular weight of PVP particularly influenced the size of the synthesized <TEX>$2SnO{\cdot}(H_2O)$</TEX> powders. A holding time of 1 hr in air at <TEX>$500^{\circ}C$</TEX> sufficiently transformed the <TEX>$2SnO{\cdot}(H_2O)$</TEX> into <TEX>$SnO_2$</TEX> phase; however, most of the PVP (molecular weight: 1,300,000) surface-capped powders decomposed and was removed after heating for 1 h at <TEX>$700^{\circ}C$</TEX>. Hence, heating for 1 h at <TEX>$500^{\circ}C$</TEX> made a porous <TEX>$SnO_2$</TEX> film containing residual PVP, whereas dense <TEX>$SnO_2$</TEX> films with no significant amount of PVP formed after heating for 1 h at <TEX>$700^{\circ}C$</TEX>.