Synthesis and characterization of homogeneous lead-substituted tin oxide with the (110) face of rutile structure
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Kenji Tabataa) and Eiji Suzuki Research Institute of Innovative Technology for the Earth (RITE), Kizugawadai, Kizu-cho, Soraku-gun, Kyoto 619-0292, Japan, and Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Takayama-cho, Ikoma-shi, Nara 630-0101, Japan (Received 10 March 2000; accepted 3 August 2000)
Synthesis of a rutile-type lead-substituted tin oxide with (110) face was investigated. The characterization was performed by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, infrared spectroscopy, x-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller surface area measurements. The homogeneous rutile-type lead-substituted tin oxide was obtained until 4.1 mol% of tin was substituted with lead. The surface of obtained oxide had a homogeneously lead-substituted (110) face.
The most thermodynamically stable (110) face of a rutile-type tin dioxide, SnO2, plays an important role in its use in many technologically important areas such as gas sensing1–6 and oxidation catalysis7–13 because it has been revealed to have unique surface properties such as the activation of molecular oxygen to several active oxygen species (such as O−, O22−, and O2−)14–18 on (110) face and the ability of oxygen desorption at relatively low temperature.15,19,20 In general, the utilization of reproducible oxygen species on the surface of oxides for oxidation reactions is a rewarding goal under fixed reaction conditions. In addition, the lowering of reaction temperature is a key requirement for the selective oxidation reactions of methane because high temperatures and pressures lead to successive oxidation to COx. Therefore, the presence of active oxygen species (O−) is quite important for the oxidation reactions because it makes it possible to initiate the oxidation reaction at low temperatures. However, the activity was still low because only a small amount of active oxygen species were formed on the surface of SnO2.18 To improve the electronic states of surface oxygen species formed on (110) face of SnO2, we tried to synthesize a rutile-type lead-substituted tin oxide. It was expected that the properties of surface oxygen species could be changed by replacing tin atoms with lead atoms, a)
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J. Mater. Res., Vol. 15, No. 10, Oct 2000 Downloaded: 16 Apr 2015
which are the same IVB group metals, because their ionic crystal radii are larger than those of tin. The important requirements for synthesis of lead-substituted tin oxide are as follows: (i) The rutile-type structure is maintained having its dominant facets, (110),21,22 and (ii) lead atoms are homogeneously solubilized in SnO2 structure. The synthesis of lead-containing tin oxide with a perovskite structure, for example, Pb2SnO423,24 and PbSnO325 has been reported. However, the synthesis of rutile-type lead-containing tin oxide with (110) face has never been reported. In thi
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