Elastic Properties of Mullite

Abstract

Using ultrasonic methods, we determined the ambient‐temperature elastic constants of dense (99.7%) hot‐pressed polycrystalline 3:2 mullite (3Al 2 O 3 2SiO 2 ). We report the usual polycrystal elastic constants: Young's, shear, and bulk moduli, and the Poisson's ratio (nu). The Poisson's ratio (nu = 0.280) suggests interatomic bonding that is very different from that of either alumina or silica. Temperature dependences of the elastic constants show a strong irregularity; for example, nu decreases as the temperature increases. This irregularity suggests an internal‐state change that is perhaps related to the incommensurate structural modulation.