Phenomenology of ferroelectrics with rotated octahedra
- 1 May 1975
- journal article
- research article
- Published by Taylor & Francis in Philosophical Magazine
- Vol. 31 (5) , 1159-1175
- https://doi.org/10.1080/00318087508226835
Abstract
Many perovskites go through transitions caused by the condensation of zone boundary modes in which the octahedra rotate around axes parallel to 〈100〉 of the cubic high-temperature phase. Some phase transitions are caused by the condensation of ferroelectric zone centre modes as well as by these octahedral rotational modes. A phenomenological theory of such ferroelectrics is presented, based on Landau's theory of second-order or continuous phase transitions, and the postulated free energy expansion is applied to the NaNbO3–KNbO3 system. The phase diagram is calculated and compared with experiment.Keywords
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