Nanohardness and brittleness of irradiated spinel ceramics

Abstract : The influence of the size of crystalline regions on mechanical properties of irradiated oxides has been studied using magnesium aluminate spinel MgAl₂O₄. The samples characterized by different dimensions of crystalline domains, from sintered ceramics with grains of few micrometers in size up to single crystals, were used in the experiments. The samples were irradiated at room temperature with 320 keV Ar²⁺ ions up to fluences reaching 5 × 10¹⁶ cm⁻². Nanomechanical properties were measured by using a nanoindentation technique and the resistance to crack formation by measurement of the total crack lengths made by Vickers indenter. The results revealed: correlation of nanohardness with accumulated damage, radiation-induced hardness increase in grain-boundary region and significant improvement of material resistance to crack formation.