AbstractThe mechanism of concentration quenching of the Gd3+ emission in (La, Gd)AlO3 and the Eu3+ emission in (Eu, Gd)AlO3 is reported and discussed. Nearest and next‐nearest neighbors are involved in the concentration quenching process. Nearest neighbor transfer occurs by exchange interaction. Even for next‐nearest neighbors this type of interaction seems to dominate. In GdAlO3 energy migration via the 6I level is reported. After excitation of the 6I level, the excitation energy migrates at 300 K about 1350 steps over the 6I level before nonradiative decay to the 6P level occurs. The energy migration in EuAlO3 at low temperatures can be described with a phonon‐assisted process.