Pressure-induced structural modifications of rare-earth hafnate pyrochlore.

Complex oxides with the pyrochlore (ABO) and defect-fluorite ((A,B)O) structure-types undergo structural transformations under high-pressure. Rare-earth hafnates (AHfO) form the pyrochlore structure for A  =  La-Tb and the defect-fluorite structure for A  =  Dy-Lu. High-pressure transformations in AHfO pyrochlore (A  =  Sm, Eu, Gd) and defect-fluorite (A  =  Dy, Y, Yb) were investigated up to ~50 GPa and characterized by in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD).