Preparation of Aluminum Oxynitride by Nitridation of a Precursor Derived from Aluminum–Glycine Gel and the Effects of the Presence of Europium

Spinel-type AlON, Al_2.75□_0.25O_3.74N_0.26, was obtained by ammonia nitridation of an oxide precursor prepared by peptizing a glycine gel with aluminum nitrate. To achieve crystallization, the nitrided product had to be annealed at 1500°C for 10 min in flowing nitrogen. The use of glycine instead of citric acid was important for obtaining a white product without residual carbon. A similar preparation method was used for adding small amounts of europium below 10 mol%. A strong blue emission was observed for products ranging from 0.5 to 3.0 mol% Eu doping. The product with 0.5 mol% doping had a maximum emission intensity at 400 nm for an excitation of 254 nm. The products with 1 and 3 mol% doping showed double maxima at 475 and 520 nm. These three emissions were due to the presence of divalent europium in the EuAl₁₂O₁₉ magnetoplumbite-like aluminum oxynitride impurity mixed with the AlON spinel major phase. The 1 mol% Eu-doped product exhibited expanded hexagonal lattice parameters ( a =0.5591 and c =2.236 nm) compared with the values for EuAl₁₂O₁₉ magnetoplumbite itself, observed in the 7.7 mol%-doped product without any strong emission. The above spectrum change was discussed in relation to the coordination around Eu²⁺.