Dielectric Properties and Phase Transitions in Some Oxyfluorides with the MeO_xF_6-x (x = 1, 2, 3) Anion in Structure

Abstract

In order to understand the role of central atom in the nature of phase transitions in two series of ammonium oxyfluorides, A₂MeO₂F₄ and A₂A′MeO_xF_6-x, the permittivity was studied in wide temperature range. In most cases structural distortions are associated with the ferroelasticity. The ferro- and antiferroelectric properties were revealed only in molybdates.

Keywords:

• Phase transitions
• permittivity
• oxyfluorides
• ferroelectrics
• ferroelastics

PACS:

• 64.70.K-
• 77.22.-d
• 77.80.-e

Acknowledgments

This work was supported by Russian Foundation for Basic Research (Grant N09-02-00062).