Low temperature, high pressure thermo-physical and crystallographic properties of KZnF3 perovskite

Abstract

The thermoelastic, and low temperature and high pressure crystallographic properties of the cubic perovskite KZnF3 have been investigated at 41 temperatures between 7 K and 305 K, and at 19 pressures between 0.07 and 6.38 GPa. Using supplementary literature values of the low temperature isobaric heat capacity, the thermoelastic properties of KZnF3 are well described by the two-term Debye model of Barron with characteristic temperatures 281 K, and 440 K, and mean Grüneisen constant of 1.43. The isothermal bulk modulus has been determined from a Birch-Murnaghan second order equation-of-state as 81.2 GPa, in excellent agreement with prior measurements of the elastic stiffnesses. The measured bulk modulus is consistent with the approximate linear trend with inverse molar volume that has been observed in other AIBIIF3 perovskite-structured compounds. Despite the simplicity implicit in the two-term model, the calculated phonon density of states has features in common with the full vibrational density of states calculated from the measured phonon dispersion curves.