Ferroelectric phase transition in Li2Ge7O15investigated by Mössbauer diffraction

Abstract

Mössbauer diffraction experiments were performed on a single crystal of lithium heptagermanate in the temperature range 250–350 K. The high energy resolution of resonant γ radiation was used to separate elastically and inelastically scattered components. A lattice expansion along c and a decrease of the intensity of the elastically scattered radiation (IBragg) connected with an increase of the intensity of the inelastically scattered radiation (ITDS) are observed at the transition from the para- to the ferroelectric phase at 283.5 K. The experimentally determined maximum of ITDS/lBragg appearing at the phase transition is much more pronounced in comparison with that predicted from TDS-correction programs, which are based on the lattice dynamical theory restricted to acoustic phonons only.