PREPARATION AND CRYSTAL-STRUCTURE OF A NEW PRASEODYMIUM MANGANESE GERMANATE - PRMNOGEO4

A new germanate, PrMnOGeO4, was synthesized and its structure was dete rmined from single crystal X-ray diffraction. PrMnOGeO4 crystallizes i n the triclinic space group <P(1)over bar> with a 5.636(1) Angstrom, b = 5.706(1) Angstrom, c = 6.941(1) Angstrom, alpha = 106.14(1)degrees, beta = 99.43(1)degrees, gamma = 107.15(1)degrees, Z = 2, and R = 0.02 52. The compound consists of infinite chains of staggered, trans-corne r-sharing MnO6 octahedra linked by GeO4 tetrahedra in a distorted tita nite structure. Channels between the chains of octahedra are filled wi th edge-shared units of 8-coordinate Pr. This new phase is described i n the context of other chain compounds including titanite, KTP, and th e MOXO(4) hydrates. Although the octahedral chains of PrMnOGeO4 do not display the short manganese-oxygen contacts characteristic of the tit anyl group in titanite and KTP, the formula is written as such for com parison with other compounds described in the literature. (C) 1995 Aca demic Press, Inc.