The elastic moduli of ScAlO3 perovskite, a very close structural analogue for MgSiO3 perovskite, have been measured between 300 and 600 K using high precision ultrasonic interferometry in an internally heated gas-charged pressure vessel. This new capability for high temperature measurement of elastic wave speeds has been demonstrated on polycrystalline alumina. The temperature derivatives of elastic moduli of Al2O3 measured in this study agree within 15% with expectations based on published single-crystal data. For ScAlO3 perovskite, the value of (partial differentialK(S)/partial differentialT)(P) is - 0.033 GPa K-1 and (partial differentialG/partial differentialT)(P) is -0.015 GPa K-1. The relative magnitudes of these derivatives agree with the observation in Duffy and Anderson [Duffy, T.S., Anderson, D.L., 1989. Seismic velocities in mantle minerals and the mineralogy of the upper mantle. J. Geophys. Res. 94, 1895-1912.] that ζ(partial differentialK(S)/partial differentialT)(P)ζ is typically about twice ζ(partial differentialG/partial differentialT)(P)ζ. The value of (partial differentialK(S)/partial differentialT)(P) for ScAlO3 is intermediate between those inferred less directly from V(P,T) studies of Fe-free and Fe- and Al-bearing MgSiO3 perovskites [Wang, Y., Weidner, D.J., Liebermann, R.C., Zhao, Y., 1994. P-V-T equation of state of (Mg,Fe)SiO3 perovskite: constraints on composition of the lower mantle. Phys. Earth Planet. Inter. 83, 13-40; Mao, H.K., Hemley, R.J., Shu, J., Chen, L., Jephcoat, A.P., Wu, Y., Bassett, W.A., 1991. Effect of pressure, temperature and composition on the lattice parameters and density of (Mg,Fe) SiO3 perovskite to 30 GPa. J. Geophys. Res. 91, 8069-8079; Zhang, Weidner, D., 1999. Thermal equation of state of aluminum-enriched silicate perovskite. Science 284, 782-784]. The value of ζ(partial differentialG/partial differentialT)ζ(P) for ScAlO3 is similar to those of most other mantle silicate phases but lower than the recent determination for MgSiO3 perovskite [Sinelnikov, Y., Chen, G., Neuville, D.R., Vaughan, M.T., Liebermann, R.C., 1998. Ultrasonic shear wave velocities of MgSiO3 perovskite at 8 GPa and 800K and lower mantle composition. Science 281, 677-679]. Combining the results from the previous studies and current measurements on ScAlO3 perovskite, we extracted the parameters (q and γ0) needed to fully specify its Mie-Gruneisen-Debye equation-of-state. In this study, we have demonstrated that acoustic measurements of K(S)(T), unlike V(P,T) data, tightly constrain the value of q. It is concluded that ScAlO3 has 'normal' γ0 (~ 1.3) and high q (~ 3.6). The high value of q indicates that ScAlO3 has very strong intrinsic temperature dependence of the bulk modulus; similar behaviour has been observed in measurements on Fe- and Al-bearing silicate perovskites (Mao et al., 1991; Zhang and Weidner, 1999). (C) 2000 Elsevier Science B.V. All rights reserved.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Physics and Astronomy (miscellaneous)
- Space and Planetary Science