Pressure-induced order–disorder transition in Gd(1.5)Ce(0.5)Ti(2)O(7) pyrochlore

An experimental study on ordered pyrochlore structured Gd(1.5)Ce(0.5)Ti(2)O(7) [Formula: see text] was carried out up to 45 GPa by synchrotron radiation X-ray diffraction and Raman spectroscopy. Experimental results show that Gd(1.5)Ce(0.5)Ti(2)O(7) transfers to a disordered cotunnite-like phase (Pnma Z = 4) at approximately 42 GPa. Compared with the end member Gd(2)Ti(2)O(7), the substitution of Ce(3+) for Gd(3+) 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 r(A)/r(B) 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 Gd(1.5)Ce(0.5)Ti(2)O(7) as a function of pressure demonstrates its compression behaviour is rather complex.