Crystallographic properties of the Ce1−xLuxO2−x/2 system at pressures up to 7 GPa

Abstract

Synchrotron powder diffraction measurements were performed up to 7 GPa on Ce1−xLuxO2−x/2 bulk samples in order to elucidate the high pressure structural properties of the system. In the studied pressure range Ce1−xLuxO2−x/2 does not show any structural phase transition. The bulk modulus as a function of the Lu content is found to broadly fall into two regimes, namely an increasing trend for 0 < x < 0.2 and a linear decrease for 0.2 ≤ x ≤ 0.4. This twofold compressibility behavior is mostly driven by two competing factors, namely the mean atomic volume for x ranging between 0.2 and 0.4, and the lattice volume at lower Lu content. Present results suggest that oxygen vacancies affect the bulk modulus value mainly above x ~ 0.2. Since pressure effects are known to be correlated to the strain acting on a thin film of similar composition, this study contributes to clarify the functional properties of doped ceria systems, such as the increased ionic conductivity of thin films subjected to a tensile strain.