Crystal structures and polymorphism in compounds Bi_6+xT

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• 作者：Nachiappan Arumugam ; Vincent Lynch ; Hugo Steinfink
• 关键词：Crystal structure ; Bismuth transition metal phosphates ; Polymorphism of bismuth transition metal phosphates
• 刊名：Journal of Solid State Chemistry
• 出版年：2008
• 出版时间：September 2008
• 年：2008
• 卷：181
• 期：9
• 页码：2313-2317
• 全文大小：540 K

文摘

The compounds Bi_6+xT_1−xP₂O_15+y, T=Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn and Pb display five polymorphic forms. Polymorph A is formed by the Ti, Mn, Fe and Ni phases. Polymorph B is exhibited by Co and Cu compounds. The Cr phase crystallizes as polymorphic form C and the Zn phase crystallizes as polymorph D. The Pb compound crystallizes in a new structure type designated as polymorph E. The transition metal crystal structures demonstrate a similar motive. OBi₄ tetrahedra share edges to form two-dimensional Bi₂O₂ layers that are spanned by PO₄ tetrahedra and TO_6−y octahedra, pyramids and a trigonal bipyramid to form a three-dimensional network. Polymorph A crystallizes in space group C2; polymorph B is centrosymmetric with space group C2/c, the unit cell parameters differ and the unit cell volume is about double. Polymorph C crystallizes in space group and polymorph D exhibits space group C2. Bi_6.4Pb_0.6P₂O_15.2 can be considered as polymorph E, space group C2, with a new crystal structure but related stoichiometry.