The manganese-induced O− centres in yttrium aluminium garnet

The models of manganese-induced coloration centres in YAG crystals described in previous papers are more exactly specified. It is shown that apart from the described Mn-O− centres (absorption 350 nm) and the Mn-O− centres (absorption 400 nm) Mn-O− centres additionally occur which in comparison to those previously described must have a somewhat modified structure. It is found by an exact analysis of the absorption and fluorescence spectra of the thermal stepwise bleaching as well as by the statistical observation of differently grown YAG crystals that these centre types largely coexist. This coexistence explains the unsymmetry and structure of the coloration bands and corroborates the concept that the coloration centres in YAG:Mn consist of at least three structure elements, namely, the impurity ion, O−, and vacancies (say O) which are differently formed.