Structural research of rare-earth oxides and the related materials

本研究项目从晶体结构的角度研究了过渡金属氧化物，特别是在高温下表现出明显氧扩散的稀土金属氧化物，如：Zr&lt；O2&gt；-&lt；Ln_2&gt；&lt；O_3&gt；除上述化合物外，还用X射线和中子衍射法研究了具有阳离子导电性的复合氧化物&lt；KxWO_3&gt_3的晶体结构，一种新的Sr-Fe-O系晶相，以及在深部地幔中起重要作用的镁硅酸盐高温高压相等。具体内容如下：(1)结合高温产品合成工程，设计了可提高2500℃以上温度的感应炉(设在大阪大学ISSR)。并成功地在真空条件下，用碳坩埚将温度提高到2700℃以上。然而，在获得淬火产品方面仍然存在一些问题。(2)用飞行时间单晶中子衍射法研究了稳定化氧化锆在高温和外加电场中的氧行为。高温下沿-lt；111&gt；观察到显著的各向异性热振动，在外加电场作用下还观察到了沿-lt；100&gt；的热振动。(3)合成产物&lt；sr_4&gt；&lt；Fe_6&gt；&lt；O_(13)&gt；与&lt；α&gt；--lt；α&gt；-&lt；Fe_2&gt；&lt；O_3&gt；经结构测定为新的钙钛矿衍生物。通过对Sr-Fe-O系统的进一步研究，有望获得更有趣的磁性质。(4)用单晶X射线衍射法研究了在27 GPa1830℃下合成的钙钛矿型镁硅钙钛矿结构。Mg&lt；O_(12)&gt；多面体变形严重，Si&lt；O_6&gt；呈正八面体。对铁在结构中的行为的认识将是一个未来的问题。除(1)-(4)外，还研究了几种氧化物的晶体结构。

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.