Pressure Dependence of the Crystal Structure of SrCeO3 Perovskite.

Abstract The crystal structure of SrCeO 3 perovskite, orthorhombic, space group Pmcn , has been determined from Rietveld profile refinement of neutron, time-of-flight, powder diffraction data at four pressures between 0 and 7.9 GPa. The unit cell compression behaviour is anisotropic with κ a  = 3.14(8) × 10 −3  GPa −1 , κ b  = 3.18(8) × 10 −3  GPa −1 and κ c  = 1.78(6) × 10 −3  GPa −1 , and fitting the pressure dependence of the unit cell volume using a second-order Birch–Murnaghan equation of state, the bulk modulus has been determined as 110.1(6) GPa. Contrary to a model based on EXAFS results, which predicts octahedral tilting as the dominant compression mechanism in perovskites with excess A-site volume, SrCeO 3 undergoes bond compression with increasing pressure in agreement with the results obtained in a recent Raman investigation. SrCeO 3 behaves atypically when compared to other A II B IV O 3 perovskites in both temperature and pressure, which is attributed to the magnitude of the Ce O bond length.