[en] Temperature dependence of the non-radiative relaxation of the octahedral coordinated Cr³⁺ ion in two laser crystals--LiCaAlF₆ and Al₂O₃--has been considered using two models of non-radiative transitions. The model of linear electron-phonon interaction, which considers collective vibrations of the crystal lattice, and the oscillating field model, which takes into account the local vibrations of an impurity center only, have been used to calculate the transition probabilities of non-radiative transitions. The obtained results have been compared with experiments