A Raman scattering study of the phase transition in the (NH4)3WO3F3 oxyfluoride

Abstract

The Raman scattering spectra of polycrystalline samples of the (NH4)3WO3F3 perovskite-like oxyfluoride were measured at frequencies of 70–3600 cm−1 in the temperature range 93–323 K, including the transition from the orientationally disordered cubic phase to the low-symmetry phase. Transitional anomalies in the spectral parameters were revealed in the frequency ranges of internal vibrations of the ammonium ions and WO3F3 octahedral groups. An analysis of the experimental results allowed the conclusion that the phase transition under study is associated primarily with the ordering of the octahedral groups.