Ferroelastic phase transition in lithium niobate and lithium tantalate under high pressure
Abstract
Lithium Niobate (LN) and Lithium Tantalate (LT) crystals at the atmospheric pressure undergo ferroelectric phase transition at temperatures about 1485 K and 930 K respectively. This contribution reports about our study of LN, LT and ruby crystals after the compression in a high pressure apparatus of lens type filled with graphite powder and heated by an electric discharge through the graphite. Paramagnetic probes, x-ray structural analysis, and optical polarization microscopy were used to register the lattice transformations. It was found that three new domains appeared after the compression. They have the same trigonal lattice but their z-axes were turned on 103 degrees relative to the z-axis of initial single-domain samples. The theoretical analysis showed a sequence of phase transitions in these crystals and symmetries of condensed soft modes. The applied high pressure under heating switches a strain of ferroelastic domains just as electric field switches a polarization of ferroelectric domains. The observed different ratio of domain volumes for samples placed perpendicular or parallel to lens axis proves evident anisotropy of hydrostatic compression in the high pressure apparatus.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARS21005M