X-ray diffraction, thermal analysis, and Raman scattering study ofK2BeF4and comparison to other members of the

Xavier Soláns

¹

,

C. González-Silgo

²

,

Teresa Calvet

³

et al.

Abstract

Thermal analysis, powder diffraction, and Raman scattering as a function of the temperature were carried out on K 2 BeF 4 . Moreover, the crystal structure was determined at 293 K from powder diffraction. The compound shows a transition from Pna2 1 to Pnam space group at 921 K with a transition enthalpy of 5 kJ/mol. The transition is assumed to be first order because the compound shows metastability. Structurally and spectroscopically the transition is similar to those observed in ͑NH 4 ͒ 2 SO 4 , which suggests that the low-temperature phase is ferroelectric. In order to confirm it, the spontaneous polarization has been computed using an ionic model. ͓S0163-1829͑98͒00309-9͔