Relation of Single‐Crystal Elastic Constants to Polycrystalline Isotropic Elastic Moduli of MgO

The three elastic compliance coefficients of synthetic periclase were determined in the kilocycles per second frequency range by a resonance method. Polycrystalline elastic moduli on dense‐formed MgO were measured. The calculated isotropic elastic moduli for polycrystalline MgO obtained from the single‐crystal constants are in good agreement with experimental values measured on the dense MgO at the theoretical density point. The measured Young's modulus and the shear modulus of polycrystalline MgO are found to be 30.50 and 12.90 × 10 11 dynes per cm 2 respectively. The results of the present investigation are compared with the earlier work in the megacycles per second frequency range. A theoretical analysis is made to establish the validity of the present values. Schemes of averaging the single crystalline elastic constants for polycrystalline behavior are reviewed for crystals of cubic symmetry.