Solid solution of metal oxides in the zirconolite phase CaZrTi2O7. I. Heterotype solid solutions
Solid solution of metal oxides in the zirconolite phase CaZrTi2O7. I. Heterotype solid solutions
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DOI：
10.1016/0022-4596(92)90286-5
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发表时间：
1992-07
影响因子：
3.3
通讯作者：
H. Rossell
中科院分区：
文献类型：
--
作者：
H. Rossell
基于粉末X射线衍射强度的结构细化已经进行了锆英石相含有10%（摩尔）的各种氧化物在固溶体。溶质阳离子的晶体学位置并不总是可能的，但它表明，大的阳离子Thiv，Ndiii，Gdiii，Ybiii和Sciii取代Caii和Zrivin的结构，和较小的Feiii，Coii，Meso，Tav和Sniv取代Tiiv，而一些交换Tiiv和Zriv也发生。有证据表明，阳离子和阴离子阵列在这些固溶体中是完整的，因此总的化学计量总是M4O7，即，取代阳离子的形式电荷是相互依赖的。结果表明，只有当Zrivis同时被较低电荷的阳离子取代时，该结构才能容忍Ndiior Thiv取代CaII，例如，医生：如果这些不可用，则适量的TiIII在结构中变得稳定，并且这可以由反应混合物中适当过量的TiO 2提供。异型固溶体的程度尚未探索：然而，在Sniv的情况下，Tiiv的替代可以是完全的。讨论了在高溶质浓度下形成的菱面体亚结构的锆英石相关相。
Structure refinement based on powder X-ray diffraction intensities has been carried out on zirconolite phases containing ∼10 mole% of various oxides in solid solution. Unambiguous crystallographic location of solute cations was not always possible, but it is shown that the large cations Thiv, Ndiii, Gdiii, Ybiii, and Sciiisubstitute for Caiiand Zrivin the structure, and that the smaller Feiii, Coii, Mgii, Tav, and Snivsubstitute for Tiiv, while some exchange of Tiivand Zrivalso occurs. There is evidence that both cation and anion arrays are intact in these solid solutions, so that the overall stoichiometry is alwaysM4O7, i.e., the formal charges of substituting cations are mutually dependent. It is shown that the structure will tolerate substitution of Ndiiior Thivfor Caiionly if Zrivis simultaneously substituted by cations of lower charge, e.g., Sciiior Mgii: if these are not available, an appropriate amount of Tiiiibecomes stabilized in the structure, and this may be supplied from a suitable excess of TiO2in the reaction mixture. The extent of the heterotype solid solutions has not been explored: however, in the case of Sniv, substitution for Tiivcan be complete. Zirconolite-related phases with rhombohedral substructure that form at high solute concentrations are discussed.