Structure of two new K2SnX(PO4)3 (X = Cr,In) langbeinite-type phases

Structures of two k2snx(po4)3 (x= cr,in) phosphates,obtained by conventional solid state reaction techniques at 950 °c,were determined at room temperature from x-ray powder diffraction (xrd) using the rietveld analysis. the two materials exhibit the langbeinite-type structure (p213 space group,z = 4). cubic unit cell parameter values are: a = 9.8741(1) å and a = 10.0460(1) å for k2sncr(po4)3 and k2snin(po4)3 respectively. final rietveld refinements lead to acceptable reliability factors (e.g.,rwp = 9.1%; rb = 5.2% for k2sncr(po4)3 and rwp = 8.1%; rb = 5.1% for k2snin(po4)3). langbeinite frameworks are principally built of sn(x)o6 octahedra sharing corners with po4 tetrahedra. structural refinements show that the two crystallographically independent octahedral sites (of symmetry 3) have a mixed sn/x (b = cr,in) population. the two potassium cations occupied large isolated cages within the framework. © 2017,university of mohammed premier oujda morocco.