High temperature neutron diffraction study of sodium di-tin tri-phosphate

Abstract

High temperature high resolution neutron diffraction study of the crystal chemistry of NaSn 2(PO 4) 3 has been completed, at four different temperatures, applying the Rietveld method to the experimental neutron diffraction profile of a synthetic crystalline powder. Below the phase transition (∼860 K) the space group has been determined to be R3̄ which changes to R3̄c in the high temperature phase. No chemical bond breaks through the transition. The change in temperature makes the SnO 6 polyhedra rotate around the three fold axis in both structures. The PO 4 polyhedra rotate strictly around the two fold axis in the high temperature phase, but around the [0001] direction in the low temperature form.