Verification of the elastic constants for α-Al₂O₃ using high-resolution neutron diffraction

Precise lattice strains measured using high-resolution neutron diffraction from a solid polycrystalline sample are used to explore the single-crystal elastic constants of α-Al₂O₃ (corundum). The analysis confirms a recent suggestion that, contrary to the long-accepted view, the sign of s₁₄ should be negative. It also indicates that the magnitude of s₁₃ should be adjusted from −0.38 × 10⁻¹² to −0.47 × 10⁻¹² Pa⁻¹. It is found that, micromechanically, the polycrystal responds to stress in a manner very close to the Reuss limit. The results confirm the applicability of the diffraction method, which could prove useful when other techniques give ambiguous results.