Date Published: August 01, 2009
Publisher: International Union of Crystallography
Author(s): Ivan V. Ogorodnyk, Igor V. Zatovsky, Nikolay S. Slobodyanik.
Potassium yttrium hafnium tris(orthophosphate) belongs to the langbeinite-family and is built up from [MO6] octahedra [in which the positions of the two independent M sites are mutually occupied by Y and Hf in a 0.605 (10):0.395 (10) ratio] and [PO4] tetrahedra connected via vertices into a three-dimensional framework. This framework is penetrated by large closed cavities in which the two independent K atoms are located; one of the K atoms is nine-coordinated and the other is 12-coordinated by surrounding O atoms. The K, Y and Hf atoms lie on threefold rotation axes, whereas the P and O atoms are located in general positions.
For the structure of the mineral langbeinite, see: K2Mg2(SO4)3 (Zemann & Zemann, 1957 ▶). For powder diffraction investigations and Rietveld refinements of phosphate-based langbeinites, see: K2MZr(PO4)3, M = Y, Gd (Wulff et al., 1992 ▶); K2FeZr(PO4)3 (Orlova et al., 2003 ▶); K2LnZr(PO4)3, Ln = Ce—Lu (Trubach et al., 2004 ▶). Hafnium-containing phosphate langbeinites are reported for K2BiHf(PO4)3 (Losilla et al., 1998 ▶) and K1.93Mn0.53Hf1.47(PO4)3 (Ogorodnyk et al., 2007a ▶). For the synthesis of zirconium- or hafnium-containing langbeinite-related phosphates from fluoride precursors using flux techniques, see: Ogorodnyk et al. (2007a ▶,b ▶). Parameters needed to calculate bond-valence sums were taken from Brown & Altermatt (1985 ▶) and Brese & O’Keeffe (1991 ▶), respectively. For ionic radii, see: Shannon (1976 ▶). For crystallographic background, see: Boultif & Louër (2004 ▶).