THE PHASE TRANSITIONS AND CRYSTAL STRUCTURES OF A NEW COMPOUND—-Sr2CaWO6

The phase transitions of the new compound SrCaWOhave been investigqted by means of DTA. X-ray powder diffraction, prceise measurement of lattice parameters and other mothods. It has been discovered that the compuund has a displaeive phase trasnition of the first order. The low temperature phase, a-SrCaWO, belong’s to orthorhombie evystal system, with space group Pmm2. lattice parameters at foom temperature are: a=8.2033 b=5.767 and e=5.8489, the measured density is D=5.981 g/cm. and each unit cell contains two formula weight. The high temperature phase, β-SrCaWO, belongs to the cubic system, with spaqce group Fm3m and tho lattice paramcter is a=8.308,at 900℃; z=4.The eryslal structures of a-SrCaWOand β-SrCaWOhave been detrmined by moans of the X-ray polyerystal diffraction method. The character of the struetures and the possibilities of phase transition are diseussed.