An equation is proposed for the calculation of the strength of intercrystalline corundum materials depending on the intercrystalline interface energy and the size of the crystals. It is demonstrated that as the crystal interface keeps increasing, the strength of the material will be determined by the crystallography of particles. It is experimentally established that by increasing the Cr2O3 content in an additive introduced in the Al2O3 – Cr2O3 – ZrO2 system, it is possible to increase the strength of corundum materials by developing conditions for denser coalescence of crystals.