Silicate perovskite analogue ScAlO3: temperature dependence of elastic moduli

The elastic moduli of ScAlO3 perovskite, a very close structural analogue f or MgSiO3 perovskite, have been measured between 300 and 600 K using high p recision ultrasonic interferometry in an internally heated gas-charged pres sure vessel. This new capability fur high temperature measurement of elasti c wave speeds has been demonstrated on polycrystalline alumina. The tempera ture derivatives of elastic moduli of Al2O3 measured in this study agree wi thin 15% with expectations based on published single-crystal data. For ScAl O3 perovskite, the value of (partial derivative K-S/partial derivative T)(P ) is - 0.033 GPa K-1 and (partial derivative G/partial derivative T)(P) is -0.015 GPa K-l. The relative magnitudes of these derivatives agree with the observation in Duffy and Anderson [Duffy, T.S., Anderson, D.L., 1989, Seis mic velocities in mantle minerals and the mineralogy of the upper mantle. J . Geophys. Res. 94, 1895-1912.] that \(partial derivative K-S/partial deriv ative T)(P)\ is typically about twice \(partial derivative G/partial deriva tive T)(P)\. The value of (partial derivative K-S/partial derivative T)(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., We idner, 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, tempera ture 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., 1 999. Thermal equation of state of aluminum-enriched silicate perovskite. Sc ience 284, 782-784]. The value of \(partial derivative G/partial derivative T)\(P) for ScAlO3, is similar to those of most other mantle silicate phase s but lower than the recent determination for MgSiO3 perovskite [Sinelnikov , Y., Chen, G., Neuville, D.R., Vaughan, M.T., Liebermann, R.C., 1998. Ultr asonic shear wave velocities of MgSiO3 perovskite at 8 GPa and 800K and low er 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 gamma(0)) needed to fully specify its Mie-Gruneisen-Debye equation-of-state. In this study, we have demonstrated that acoustic measurements of K,(T), unlike V(P,T) data, tightly constrain the value of q. It is concluded that ScAlO3 has 'normal' gamma(0) (similar to 1.3) and high q (similar to 3.6), The high value of q indicates that ScAlO3 has very strong intrinsic temperature dependence of t he 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.