Abstract
The perovskite solid solutions are investigated using synchrotron x-ray diffraction and Raman spectroscopy in order to clarify the structural changes in the concentration range at room temperature. The orthorhombic antiferroelectric P phase (space group Pbma, exists up to and in the concentration interval we have confirmed a previously reported transition to the orthorhombic ferroelectric Q phase (space group It is found that the Q phase is stable up to but in the narrow concentration interval at the dominating (86.2%) rhombohedral N phase (space group coexists with the minor (13.8%) Q phase at room temperature. The crystal structure of this rhombohedral N phase has been refined using Rietveld method. Detailed comparison with similar low-temperature phase of pure showed that the octahedra are slightly distorted in the solid solution with while they are rather regular in Raman spectra showed drastic changes associated with the transition and revealed coexistence of the P and Q phases in the interval Abrupt transformation of the Raman response and remarkable narrowing of the Nb-O stretching vibrations related to the existence of the rhombohedral N phase at were observed.
- Received 9 May 2003
DOI:https://doi.org/10.1103/PhysRevB.69.144105
©2004 American Physical Society