Oxygen potential and defect structure of oxygen-excess pyrochlore Ce2Zr2O7+x

Abstract High-temperature thermodynamic study of the oxygen-excess pyrochlore-type (P-type) cerium zirconate Ce 2 Zr 2 O 7+ x has been performed by electromotive force (EMF) method in combination with the structural study by room-temperature powder X-ray diffraction (XRD) method. For this purpose, we have developed an EMF measurement system: (Pt) air |Zr(Ca)O 2− x | Ce 2 Zr 2 O 7+ x (Pt). The oxygen potential ( g (O 2 )) vs. oxygen nonstoichiometry ( x ) and temperature ( T ) relations of P-type Ce 2 Zr 2 O 7+ x were elucidated. The g (O 2 ) vs. x relation of Ce 2 Zr 2 O 7+ x was controlled and measured at 1078 K over 0 x ≤0.75 by applying the Coulomb titration method. The g (O 2 ) vs. temperature ( T ) relation was also measured for each x by performing the temperature scan down to 793 K (793≤ T ≤1078 K). It was found that the isothermal g (O 2 ) vs. x curves exhibit a terrace around x =0.5 for the measured temperature range. The powder XRD results showed that Ce 2 Zr 2 O 7+ x maintained its single pyrochlore-type structure all over 0 x a 0 ) in this system were found to decrease almost linearly with x over 0 x ≤1.