Synthesis of Tin Oxide Nanocrystalline Phases via Use of Tin(II) Halide Precursors

Nanocrystalline tin oxides are synthesized via precipitation from heated solutions as well as from a novel above-solution vapor deposition route that occurs at low temperatures and atmospheric pressure. Crystalline phases are characterized via powder X-ray diffraction. Samples precipitated from reactions of SnCl 2 are found to exist primarily as mixtures of tetragonal SnO and tetragonal SnO 2 or tetragonal SnO 2 and tin(II) oxyhydroxide (Sn 6 O 4 (OH) 4 ), depending on reaction conditions. A mixed tin(II)/tin(IV) sample is shown to produce a rarely observed form of the intermediate oxide Sn 3 O 4 upon annealing in air at 600 °C. SnBr 2 exclusively forms tetragonal SnO 2 via precipitation. Variation in the solvent composition with SnBr 2 is shown to result in vapor deposition of SnO 2 at temperatures below 160 °C. The average crystallite sizes of the vapor-deposited material are ≈3 nm and grow slowly upon heating. Partially hydrolyzed SnBr 4 is proposed as the vapor deposition intermediate based on variations in precursor/solvent combinations along with FTIR and GC-MS analysis of the reaction solution removed prior to the onset of deposition.