Lattice dynamics study of (Gd1-xYbx)(2)O-3(x=0.11) at high pressure

In this study, we report an experimental investigation of (Gd1-xYbx)(2)O-3 under high pressure by means of Raman scattering measurements complemented with ab initio calculations in pure Gd2O3. Raman spec-troscopy of compressed (Gd1-xYbx)(2)O-3 (x = 0.11) revealed a first phase transition from the cubic Ia (3) over bar phase (C-type) to the monoclinic C2/m phase (B-type) at 6.2 GPa followed by a second phase transition towards the trigonal P (3) over bar m1 phase (A-type) at 9.8 GPa. This sequence of phase transitions is different to that pre-viously reported for pure Gd2O3. A phase transition from the trigonal to the monoclinic phase is observed on downstroke, so the B-type phase remains metastable at room pressure, as observed in all C-type rare earth sesquioxides. Theoretical calculations have helped to identify the different polymorphs and to assign the symmetry of the observed first-order Raman-active modes in the three phases. The pressure coefficients of the Raman-active modes of the three phases followed under pressure have been reported and compared to those of pure Gd2O3 and other rare-earth sesquioxides.