Crystal Structure of the Glaserite Form of BaNaPO4

Abstract

Crystals of BaNaPO4 were grown from a Ba3P2O8–Na2B4O7 melt. The crystals are trigonal, space group [Formula: see text]with a = 5.622(4) and c = 7.259(5) Å. The structure, isotypic with that of glaserite, was refined by full-matrix least-squares methods to a final R value of 0.042 using 218 unique reflections. There are three different cation sites. Na and Ba lie at sites of [Formula: see text] symmetry and are coordinated to 6 and 12 oxygen atoms respectively. The Na—O bond lengths are 2.344(7) Å and the two unique Ba—O bond lengths are 2.788(7) and 3.247(9) Å. The remaining cation site has 3m symmetry, a coordination number of 10, and contains equal amounts of Na+ and Ba2+. The bond lengths range from 2.548(12) to 3.017(7) Å. The phosphate group also has 3m symmetry with mean P—O bond lengths of 1.538 Å. The underbonded apical P—O bond length is 1.520 Å.