On the mechanism of the recombination luminescence of α-Al2O3 crystals with nonstoichiometric excess of aluminium

The thermostimulated luminescence (TSL) of vacuum-annealed Al2O3 crystals is studied after selective photostimulation at LNT with light corresponding to the absorption bands of electron or hole centres. The comparison of the results obtained on as-received crystals and crystals irradiated by X-rays at 480 K before photostimulation at LNT leads to the conclusion that the TSL peaks at 100, 260, 325, and 360 K are due to electron recombination with localized holes, and the peaks at 225, 280, 370, and 415 K are due to hole recombination with localized electrons. The luminescence band at 3.0 eV is observed both, in the electron and hole recombination processes. It is suggested that the TSL after photostimulation is mainly of monomolecular character.