Phase transitions in AgTaO3single crystals

AgTaO3 single crystals have been obtained by the molten salt method; two different solvents, AgCl and V2O5, were used. X-ray investigations have been carried out in the temperature region from 300 K to 800 K. At room temperature AgTaO3 possesses a pseudocubic perovskite-type unit cell with rhombohedral distortion. Two structural phase transitions, to tetragonal at 650 K and to cubic symmetry at 770 K, have been observed. In the tetragonal phase a jump of the lattice constants has been observed at approximately 680 K. DTA and domain structure investigations confirm the presence of these phase transitions.