Elasticity and thermal expansion of a natural garnet up to 1,000K.

Abstract

High temperature mechanical properties of a natural pyrope garnet have been investigated up to 1, 000K. The elastic moduli were measured by the Rectangular Parallelepiped Resonance (RPR) method. The frequencies of the lower 16 modes smoothly decrease with temperature from 300 to 1, 000K, and so do the elastic moduli.Thermal expansion of the specimen was measured by a dilatometric method. The least squares calculation based on an equation kY2-Y+E(θE, T)/Q=0(Y is relative volume expansion, and E(θE, T) is the Debye function) yields the constants Q=16.5MJ/mol, θE=698K, and k=1.50. From these constants, the Gruneisen's parameter γ0 (=Bo Vo/Q) and the pressure derivative of bulk modulus ∂B/∂P (=2k+1) at 0K are 1.2 and 4.0, respectively.By using these data, bulk moduli and other physical properties of this garnet are estimated up to higher temperatures (Table 2).