Structural research of rare-earth oxides and the related materials

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In this research project, transition-metal oxides, in particular, rare-earth metal oxides such as Zr <O_2> - <Ln_2> <O_3> solid slution which show remarkable oxygen diffusion at high temperature, were investigated from crystal structural point of view. In addition to the above compounds crystal structures of complex oxides such as <KxWO_3> which show cationic conductions, a new crystalline phase of Sr-Fe-O system, high-temperature and high-pressure phases of magnesium-silicates which take important roles in the deep mantle, etc, were also studied by means of X-ray and neutron diffraction methods. Some of details are as follows: (1) In relation to the synthetic works of high-temperature product, an induction furnace which is capable to increase above 2500C was designed(set up at ISSR, Osaka Univ.) and was succeeded to raise temperature above 2700C, using carbon crucible and in evacuated condition. However, it remains some problems in obtaining quenched products. (2) Oxygen behaviors of stabilized-zirconia were investigated at high temperatures and in an applied electrical fields by time-of-flight single-crystal neutron diffraction method. Remarkbale anisotropic thermal vibrations were observed along <111> at high temperature, and, in addition, along <100> in an applied electrical field. (3) Synthetic product, <Sr_4> <Fe_6> <O_(13)> , at 1300C from the mixture of Sr <CO_3> and <alpha> - <Fe_2> <O_3> with ratio of 4:3 was turned out to be a new perovskite-derivative by the structure determination. An interesting magnetic properties will be expected by further investigations of Sr-Fe-O system. (4) Perovskite-type MgSi <O_3> synthesized at 27GPa and 1830C was investiagted by single-crystal x-ray diffraction method. Mg <O_(12)> polyhedon is very distorted and Si <O_6> show an regular octahedron. The knowlege of Fe behavior in the structure will be interesting as a future problem. In addition to (1)-(4), crystal structues of several oxides were also studied.