An examination of the elasticity of hot-pressed MgO

The elastic properties of polycrystalline as well as single crystal MgO have been measured extensively. New measurements on four hot-pressed magnesium oxide samples are presented and compared to existing data. Discrepancies are noted between the properties determined for the different polycrystalline MgO samples; the magnitude of these differences is as much as ±6% for the reported bulk modulus. X-ray and electron microscopy techniques were applied to the four hot-pressed specimens and revealed the presence of residual strains, plastic deformation and a preferred orientation of grains with respect to hot pressing directions. Scanning electron micrographs also indicated that a non-homogeneous pore distribution existed. The results suggest that the data obtained from polycrystalline materials may not truly reflect the intrinsic elasticity of the material but rather some combination of the elasticity of the material and the state of aggregation of the polycrystal.