Royal Society Open Science | 2019
Pressure-induced order–disorder transition in Gd1.5Ce0.5Ti2O7 pyrochlore
Abstract
An experimental study on ordered pyrochlore structured Gd1.5Ce0.5Ti2O7 (Fd3¯m) was carried out up to 45 GPa by synchrotron radiation X-ray diffraction and Raman spectroscopy. Experimental results show that Gd1.5Ce0.5Ti2O7 transfers to a disordered cotunnite-like phase (Pnma Z = 4) at approximately 42 GPa. Compared with the end member Gd2Ti2O7, the substitution of Ce3+ for Gd3+ increases the transition pressure and the high-pressure stability of the pyrochlore phase. This pressure-induced structure transition is mainly controlled by cationic order–disorder modification, and the cationic radius ratio rA/rB may also be effective for predicting the pyrochlore oxides high-pressure stability. Two isostructural transitions are observed at 6.5 GPa and 13 GPa, and the unit-cell volume of Gd1.5Ce0.5Ti2O7 as a function of pressure demonstrates its compression behaviour is rather complex.