X線回折法による非晶質三酸化タングステン薄膜の骨格構造の評価

概要

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Amorphous tungsten trioxide films were prepared from iso-polytungstic acid as a precursor and by RF magnetron sputtering method. Framework structure was investigated based on X-ray diffraction analyses, in which amplitude function as well as radial distribution function was used. And the previously reported films prepared by vacuum evaporation and an ion exchange method using Na_2WO_4・2H_2O as a precursor were also re-examined. It was found that, in the films derived from iso-polytungstic acid, the framework had a similar manner to that in hexagonal-WO_3 crystal, whose framework was constructed by 3-, 4- and 6-membered rings formed by WO_6 ocrahedra. It was supposed that edge-sharing polyhedra and tungsten and/or WO_6 defects were present in the as-prepared film and changed to corner-sharing connection and continuous framework by post-annealing. It was also suggested that structural water was present in a hexagonal tunnel in the framework. These structural characteristics were also observed in the films prepared by vacuum evaporation and ion exchange methods. As for the sputtered films, formation of two framework-types without structural water was confirmed. The hexagonal-WO_3 like framework was formed in the films prepared under a low O_2 partial pressure, and tetragonal-WO_3 like one with an ordinary ReO_3-type structure made up with 4-membered rings was produced at a high O_2 pressure.
社団法人日本セラミックス協会の論文
1995-03-01