Structural Evidence for Ferroelectricity in Eu2GeS4

Studies of the low-temperature D162h orthorhombic phase and investigation of trigonal–monoclinic phase transition in quenched high-temperature phase KIn(WO4)2 were performed by means of infrared and Raman spectroscopy. The observed vibrational modes were assigned to the vibrations of respective atoms in the unit cells. It has been shown that as a result of the trigonal–monoclinic phase transition a similar temperature dependence of vibrational modes has been observed as that found for KSc(WO4)2 although crystallographic studies suggest that the former crystal has D43d and the later D33d structure.