High temperature structural studies of Ba2BiTaO6

Synchrotron X-ray powder diffraction studies have shown that the Bi and Ta are ordered on the B-sites of the double perovskite Ba2BiTaO6. At room temperature the structure is rhombohedral R (3) over bar and this transforms to a cubic structure F m(3) over bar m near 250 degrees C. The R (3) over bar to F m(3) over bar m transition appears to be continuous. Although the temperature dependence of both the rhombohedral angle and volume strain show anomalous behavior, both are indicative of a second order phase transition. (c) 2004 Elsevier SAS. All rights reserved.