Microhardness and crack resistance of gallium oxide

The microhardness and crack resistance of two main gallium oxide polytypes: metastable $\alpha$-Ga$_{2}$O$_{3}$ with a corundum structure and $\beta$-Ga$_{2}$O$_{3}$ (high-temperature phase) with a monoclinic crystal structure, have been studied using a Vickers method of diamond pyramid indentation. As far as we know, this is the first attempt to compare the mechanical properties of the two polytypes of gallium oxide.