Spinel‐type AlON, Al2.75□0.25O3.74N0.26, 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+.
RE 2O2CN2 (RE = La, Eu, and Gd) and Eu-doped RE2O2CN2 (RE = La and Gd) phosphors were prepared by nitridation of oxide precursors through rare earth citrate gel. This preparation method increased the doping limit to 20 atom % in La2O2CN2. The value was considerably wider than 7 atom % of solid-state synthesis through rare earth oxide. Eu-doped Gd2O2CN2 was firstly synthesized by this method. The shape of luminescence spectra and luminescence intensity were different between these oxycyanamides reflecting the difference in their crystal structure and crystallinity.
Two strontium cyanamide polymorphs trigonal low temperature phase and orthorhombic high temperature phase were prepared by firing strontium acetate in ammonia flowing at 600-850? C. Trigonal low temperature phase irreversibly changed to orthorhombic high temperature phase by post annealing. The two structures differed in SrN 6 octahedon linkage and NCN 2 arrangement. The structural change was discussed in relation to repulsion between strontium cations and SrN 6 octahedron linkage by corner or edge sharing.
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