High temperature x-ray single crystal study of Na1/2Bi1/2TiO3

For a Na0.5B0.7TiO2 single crystal the intensity variation of the satellite reflection was measured by X-ray diffraction. No hystereses were observed for the phase transitions into both the rhombohedral and the tetragonal phases, however there is a coexistence of both phases in the range between similar to 250 degrees C and 300 degrees C. By fitting the intensity vs. temperature curve for the tetragonal phase a critical exponent of 2 beta = 0.39(4) was obtained. The mean square displacement of the probability tensor of the high temperature cubic phase does not vary linearly with temperature which indicates that there is some disorder in this phase.