Phase Transitions in Oxides, Fluorides and Oxyfluorides with the Ordered Perovskite Structure

Abstract

Some results of calorimetric and structural investigations of the A ₂ A′ MO _x F _{6 − x} crystals series with the elpasolite-cryolite structure are reported. The analysis has exhibited a key role of the MO _x F _{6 − x} species content in the disordering degree and stability of Fm3m phase as well as in the nature of structural distortions.

Keywords:

• Phase transitions
• ordered perovskites
• entropy
• electron density

PACS:

• 61.50.Ks
• 65.40.Ba
• 65.40.Gr

Acknowledgment

This work was supported by Russian Foundation for Basic Research (Grant N 06-02-16102a).