Nanoindentation on neutron irradiated MgO crystals

Using a nanoindentation technique, hardness and Young's modulus were determined in as-grown MgO single crystals and after neutron irradiation with different doses up to 6.9×1018 n/cm2. The resulting defects were monitored by optical absorption spectroscopy. As-grown crystals have a hardness of (9.1±0.2) GPa. After neutron irradiation, hardness increases with dose, whereas Young's modulus remains practically constant, indicating that the elastic properties are not influenced by the irradiation. For the highest neutron dose of 6.9×1018 n/cm2, the resulting value for hardness was (12.3±0.2) GPa. The recovery of radiation damage following thermal treatments is also investigated. The hardening observed in n-irradiated crystals is attributed to interstitials.