Elasticity of single-crystal wüstite at ambient and elevated temperature from resonant ultrasound spectroscopy

Abstract Results are presented from resonant ultrasound spectroscopy (RUS) measurements of adiabatic elastic moduli for single-crystal Fe 0.943 O at ambient and elevated temperature. Room temperature results are comparable to those obtained in four other Fe 1− x O studies that used dynamic techniques with single-crystals. These five studies together result in small ranges for the bulk ( K S ) and two shear ( C 44 and C S ) moduli of (GPa) 153–156, 45.1–46.1, and 47.7–48.0, respectively, at ambient P , T conditions. These ranges contrast with those from two other single-crystal studies with higher values for each of these elastic moduli. Our review of data from precise dynamic methods on single-crystals does not provide evidence of systematic compositional effects on K S for Fe 1− x O with x around 0.05. Our measurements from 297–500 K are the first single-crystal elasticity determinations reported for Fe 1− x O above room temperature and provide tight constraints on the temperature dependences of the shear moduli over this range. The positive value of (∂ C 44 /∂ T ) P due to the softening of C 44 at the Neel temperature, T N ∼195 K, persists to at least 500 K with extrapolations indicating it may continue to about 750 K. Magnetoelastic interactions affect the elastic state of Fe 1− x O to temperatures several hundreds of kelvin above T N .