New defect-crystal-chemistry model for non-vegardianity and non-random defect structure of defect-fluorite MO-LnO solid solutions (M=Ce, Th; Ln=lanthanide), 1; Generalized non-vegardianity analysis

欠陥蛍石型酸化物固溶体の非ヴェガード性及び複雑な欠陥構造への新しい結晶欠陥化学的アプローチ,1; 非ヴェガード性の解析

中村 彰夫

Nakamura, Akio

Lattice-parameter data of the entitled solid solutions with M=Ce and Th exhibit marked positive non-Vegardianity. Detailed analysis clarifies the generalized non-Vegardian behavior of oxygen-vacancy (V) type distortionally-dilatedsolid solutions with non-random oxygen coordination around the cations. The M=Ce and Th are similarly modestly Ln-V associative for the smallest Ln=Y and Gd and shift to the completely opposite non-randomness for the largest Ln=Nd and La, being strongly Ce-V associative in the former and extremely Ln-V associative in the latter. While, the stabilized M=Zr and Hf exhibit more complex behavior accompanying a broad lattice-parameter hump over the wide middle range. This feature is interpreted as a macroscopic signal for their intermediate pyrochlore-type ordering. The author attempts to extend the model to a more general one also applicable for the latter.