Coprecipitation synthesis of Nd:YAG nanopowders II: the effect of Nd dopant addition the on Luminescence Properties

Nanopowders of Yttrium Aluminium Garnet (Y3Al5O12, YAG) doped with neodymium (Nd:YAG, 0.2-24.0 at.%) were prepared using the co-precipitation method followed by an annealing treatment up to 950 °C. For a concentration of neodymium lower than 3.2 at.% the materials were found constituted by the garnet phase according to X-ray diffraction investigations. However, at higher neodymium loading the hexagonal and monoclinic forms of yttrium aluminium oxides were found together with the garnet phase. For Nd quantity lower than 0.8% the luminescence emission spectra appear to be nearly the same, indicating that in the examined range of composition the immediate surrounding of the emitting Nd3+ ions is independent of its concentration. For Nd quantity higher than 0.8%, the emission lines have nearly the same peak position, but the band-widths are larger and the relative line intensity increases with neodymium content. A dramatic decrease of two magnitude orders of the luminescence lifetimes occurs with the Nd quantity increase. This behaviour is ascribable to the presence of a secondary phase together with the quenching effects