Synthesis and crystal structure of novel complex phosphate Li5Cu2Al(PO4)4

A new complex phosphate Li5Cu2Al(PO4)(4) has been obtained by the flux method in the Cs-Li-Cu-V-P-O system. Its crystal structure has been determined by X-ray diffraction (R (1) = 2.74%) to be as follows: sp. gr. , a = 4.860(5) , b = 7.788(5) , c = 8.324(5) , alpha = 69.542(5)A degrees, beta = 90.016(5)A degrees, gamma = 75.318(5)A degrees, Z = 1, and V = 284.2(4) (3). The compound under study has a dense structure and a three-dimensional framework build up of [LiO5], [AlO6], [Cu/LiO5], and [CuO4] polyhedra and [PO4] tetrahedra. A comparative crystal-chemical analysis of two isotypic compounds with a general formula Li5Cu2 M(PO4)(4) (M = Fe, Al) has been performed. Topological relations between the Na2Mg5(PO4)(4) and Li5Cu2 M(PO4)(4) crystal structures, which are characterized by different cationic compositions, are revealed.