The Reaction of Rare Earth Oxides with a High Temperature Form of Rhodium(III) Oxide
The Reaction of Rare Earth Oxides with a High Temperature Form of Rhodium(III) Oxide
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稀土氧化物与高温形式的氧化铑（III）的反应
DOI：
10.1021/ic50009a023
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发表时间：
1963
影响因子：
4.6
通讯作者：
W. Croft
中科院分区：
文献类型：
--
作者：
A. Wold;R. Arnott;W. Croft
制备了含三价铑的氧化镧铑和氧化钕铑，它们具有畸变的钙钛矿结构。它们是正交晶系，可能属于空间群D2 h 16 Pbnm。晶格常数为a= 5.524 Ω.，B- 5.679 μ m，c= 7.900 A.对于LaRhO 3和α-5.402 A.，B-5.772 A.，c= 7.816。对于NdRhO。这种畸变的显著特征是a< c/V2< B，表明它可能只是由于尺寸效应。这与LaMnO观察到的畸变相反。g（c/V 2 < a< B），这是由电子有序（Jahn-Teller）和尺寸效应引起的。氧化钐和氧化钇在与制备氧化钕铑相同的条件下与氧化铑反应时都不会形成简单的钙钛矿。这意味着由于尺寸效应可能产生的最大畸变是a< c/M ~ 2 < B的类型，并且可以从电子有序化引起的畸变中排除。本文还报道了氧化铑的两种存在形式，一种是具有六方晶系结构的低温形式，另一种是与钙钛矿有关的高温形式。750 ℃以上低温形态向高温形态转化。
Lanthanum rhodium oxide and neodymium rhodium oxide, containing rhodium in the trivalent state, havebeen prepared and possess distorted perovskite structures. They are orthorhombic and probably belong to space group D2h16 Pbnm. The lattice constants are a= 5.524 Á., b— 5.679 Á,, c= 7.900 A. for LaRhOs and a— 5.402 A., b—5.772 A., c= 7.816 Á. for NdRhOs. The distinguishing feature of this distortion is that a< c/V2< b, indicating that it is probably due to a size effect only. This is in contrast to the distortion observed for LaMnO. g (c/V2< a< b) that is caused by both an electronic ordering (Jahn-Teller) and size effects. Neither samarium oxide nor yttrium oxide form a simple perovskite when allowed to react with rhodium (III) oxide under the same conditions used to prepare neodymium rhodium oxide. This implies that the maximum distortion possible dueto size effects is of the type where a< c/M2< b and can be distinguishedfrom the distortion caused by electron ordering. This paper also reports the existence oftwo forms of rhodium oxide, a hexagonal low temperature form with the corundum structure and a high temperature form apparently related to the perovskites. The low temperature form transforms to the high temperature form above 750.