The behavior of excited centers due to oxygen impurities in the AlN lattice is reported for the first time by thermoluminescence (TL), studies between 77 and 550 K after 253.7 nm UV excitation. According to the origin of the product, the TL brings to the fore important differences due essentially to the synthesis process. The measurements of fluorescence let appear emission bands around 3.2 eV identified as due to substitutional oxygen and a very narrow one at 2.1 eV characteristic of Mn4+ ions observed before by EPR measurements. At last, measurements of FTIR confirm, as supposed from TL, the presence of gamma-AlON in one of the studied samples even if it is under the form of marks only.