STUDY OF THE PHASE-BEHAVIOR OF EU2O3 UNDER PRESSURE VIA LUMINESCENCE OF EU-3+

We have investigated the phase transition of Eu2O3 under pressure from a C-type b.c.c. structure to a B-type monoclinic structure by the luminescence spectra of the Eu3+ ion. It is suggested that the luminescence from f-f transitions in Eu3+ is very sensitive to the Eu3+ ion environment and can be used as a spectral probe to identify the crystal structure. The C-to-B transition occurs at about 8.0 GPa and the B-type structure was retained after the pressure had been released. The transition thermodynamics and kinetics are discussed, and the entropy for the C-to-B transformation was estimated. It was concluded that the C type is the room temperature and pressure stable structure, whereas the B type is metastable at room temperature.