Abstract
The colorless sample of Sr 2MgWO 6 was prepared by conventional solid-state reaction of stoichiometric amounts of SrCO 3, WO 3 and MgO and characterized by powder X-ray diffraction (XRD) studies. In the temperature range of 300–15 K, detailed structural studies on Sr 2MgWO 6 were carried out by Rietveld refinements of the observed powder neutron diffraction (ND) data. At ambient temperature Sr 2MgWO 6 crystallizes in tetragonal (space group I4/ m) lattice with unit cell parameters: a = 5.5882(2) and c = 7.9452(7) Å, V = 248.11(3) Å 3, Z = 2. This tetragonal ( I4/ m) structure is retained down to 15 K. The structural analysis of the sample at different temperatures indicates no appreciable change in the Mg O and W O bond lengths. However, a decrease in the tilt angle is observed with increasing temperature. The negative thermal expansion of the c-axis is attributed to increasing transverse displacement amplitude of the bridging oxygen atoms along this axis.
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