Abstract
We report accurate temperature-dependent measurements of the optic index of refraction, the birefringence, and the strain in the ferroelectric, tungsten-bronze crystal . This composition congruently melts, so large homogeneous high-quality crystals can be grown. From the experimental data, it appears that far above the ferroelectric phase transition temperature (≊88 °C), up to a temperature (≊300 °C), the crystals appear to possess a local, randomly oriented (up or down), polarization . The values of obtained from the index and completely independent strain measurements are in very good agreement with each other, as are the values of . Various aspects of our understanding of the polarization behavior and other effects in this ferroelectric system are discussed.
- Received 17 November 1986
DOI:https://doi.org/10.1103/PhysRevB.36.2030
©1987 American Physical Society