High temperature phase transitions in A_2BX4 compounds.
Abstract
The high temperature phase transitions observed in several crystals of the A_2BX4 family from the prototype P6_3/mmc are reviewed. Experimental DSC and Raman scattering results on Rb_2WO4 point out the role of disorder in the phase transition and show a rare first order incommensurate phase transition as T is lowered. We present also an Ising like model with competing interactions that predicts the appearance of a basal plane incommensurate phase in a hcp structure. This model is applied to explain the high temperature phase transitions observed in several crystals of the A_2BX4 family, including the appearance of incommensurate phases in Rb_2WO_4, K_2WO4 and K_2MoO4 compounds. The discontinuous incommensurate phase transition in Rb_2WO4 can be explained considering a coupling between the crystal elasticity with orientation of the BX4 tetrahedra.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2000
- Bibcode:
- 2000APS..MARB19010J