Formation of a cubic Sr2MnWO6 phase at elevated temperature;: a neutron powder diffraction study

In a temperature dependent neutron powder diffraction (NPD) study we observed the high temperature cubic phase at 973 K in the polycrystalline double perovskite Sr2MnWO6. Rietveld analysis of the NPD data shows that the room temperature tetragonal phase exists up to 573 K (space group P4(2)/n, a = 8.0119 (4) Angstrom, c = 8.0141(8) Angstrom). At 773 K, the primitive tetragonal symmetry change to body-centred tetragonal (space group I4/m, a = 5.6935(5) Angstrom, c = 8.077(l)Angstrom) and finally at 973 K it becomes face-centred cubic (space group Fm-3m, a = 8.0864(8) Angstrom). The changes in the structural symmetry are connected to the small distortion of the B-site octahedra, which are insensitive to the Differential Thermal Analysis (DTA) signal. (C) 2003 Elsevier Science Ltd. All rights reserved.