Phase transition and crystal structure of a new compound - Sr2FeWO6

A new compound Sr2FeWO6 has been synthesized by solid state sintering. The phase transition of this compound was investigated by means of differential scanning calorimetry (DSC), X-ray powder diffraction, precise measurement of lattice parameters and other methods. It has been discovered that the compound has a displacive phase transition of the first order at (360+/-5)degrees C. The low temperature phase, alpha-Sr2FeWO6, belongs to tetragonal crystal system, with space group 14/m; its lattice parameters at room temperature are: a=b=0.55702 nm, and c=0.79094 nm, the measured density is D-m=6.93 g/cm(3), and each unit cell contains two formula weights. The high temperature phase, beta-Sr2FeWO6, belongs to the cubic system, with space group Fm3m and the lattice parameter is a=0.7939nm at 400 degrees C; z=4. The calculated density is D-x=6.780 g/cm(3). The crystal structures of alpha-Sr2FeWO6 and beta-Sr2FeWO6 were also determined by means; of the X-ray polycrystal diffraction method. The phase transition mechanism and the temperature are investigated.