Single-crystal neutron diffraction study of the structural phase transition in ?
Abstract
The tetragonal-to-cubic transition in ferroelectric 0953-8984/8/16/020/img11 (BCT) has been studied using a single-crystal neutron diffraction technique. The intensities of the Bragg profiles are observed to increase anomalously with temperature above 0953-8984/8/16/020/img12 are then to drop sharply before reaching the structural transition temperature 0953-8984/8/16/020/img13. The intensity variations and 0953-8984/8/16/020/img13 are sensitive to sample heating rate with 0953-8984/8/16/020/img15 at slow heating rates. Structural refinements indicate that the observed intensity variations are due to changes in the domain structure and the thermal parameters B with the latter becoming anomalously large several degrees Celsius below 0953-8984/8/16/020/img13 compared with those above 0953-8984/8/16/020/img13 and at room temperature, indicating the onset of significant pre-transition disorder for Ti ions along the polar c axis. The observed linewidths of the diffraction profiles reflect contributions from the anisotropic domain sizes and the internal strains and an added contribution from the coexistence of tetragonal and cubic phases below 0953-8984/8/16/020/img13. The results suggest that the fluctuations in the Ti positions existing well below 0953-8984/8/16/020/img13 could be responsible for the broadening of dielectric response observed for BCT.
- Publication:
-
Journal of Physics Condensed Matter
- Pub Date:
- April 1996
- DOI:
- 10.1088/0953-8984/8/16/020
- Bibcode:
- 1996JPCM....8.2905S