CoCr2Se4中的高温有序-无序转变以及单斜CoCr2Se4中的俘获无序：Cu(1-x)Co(x)Cr2Se4相的结构特征

High-temperature order-disorder transition in CoCr2Se4 and trapping co disorder in monoclinic CoCr2Se4: structural features of Cu(1-x)Co(x)Cr2Se4 phases.

作者信息

Svitlyk Volodymyr, Mozharivskyj Yurij

机构信息

Department of Chemistry, McMaster University, Hamilton, ON, Canada, L8S 4M1.

出版信息

Inorg Chem. 2009 Jun 15;48(12):5296-302. doi: 10.1021/ic900264x.

DOI:10.1021/ic900264x

PMID:19432466

Abstract

X-ray diffraction studies on the Cu(1-x)Co(x)Cr(2)Se(4) system (x = 0, 0.2, 0.4, 0.6, 0.8, 1) proved the existence of the cubic spinel-type structure for x < or = 0.2 and the monoclinic Cr(3)S(4)-type one for x > or = 0.8. CoCr(2)Se(4) undergoes an order-disorder phase transition above 750 degrees C. The high-temperature CoCr(2)Se(4) polymorph crystallizes in the filled GdI(2)-type structure with the P3m1 space group. The trigonal-to-monoclinic symmetry breaking in CoCr(2)Se(4) is found to be first-order within Landau theory. Co distribution in the low-temperature monoclinic CoCr(2)Se(4) structure depends on cooling conditions of trigonal CoCr(2)Se(4): rapid quenching results in Co disorder in the monoclinic structure, while slow cooling yields a fully ordered monoclinic structure.

摘要

对Cu(1 - x)Co(x)Cr₂Se₄体系（x = 0、0.2、0.4、0.6、0.8、1）的X射线衍射研究证明，当x ≤ 0.2时存在立方尖晶石型结构，当x ≥ 0.8时存在单斜Cr₃S₄型结构。CoCr₂Se₄在750℃以上会发生有序-无序相变。高温CoCr₂Se₄多晶型体以P3m1空间群的填充GdI₂型结构结晶。在朗道理论范围内，发现CoCr₂Se₄中从三角对称到单斜对称的破缺是一级的。低温单斜CoCr₂Se₄结构中的Co分布取决于三角CoCr₂Se₄的冷却条件：快速淬火会导致单斜结构中Co无序，而缓慢冷却会产生完全有序的单斜结构。