The size effect on luminescence properties of praseodymium doped LuAG prepared by Pechini method

Nano crystalline Pr3+(1 mol%) doped lutetium aluminium garnet was prepared by the Pechini method in the temperature range of 800-1200 °C. The size of the grains was controlled by the annealing temperature of the samples. The crystal structure was analyzed by XRD. The results showed that LuAG:Pr3+ nano crystalline powder starts to crystallize at about 850 °C, and the particle size increased with the annealing temperature. The morphology of the nano crystalline powder was investigated by TEM and showed the grains of the samples well-structured but with a tendency to agglomerate. The average size of the grains was determined to be about 10-45 nm. The EDX spectroscopy was done to identify what those particular elements are and their relative proportions in the nano crystalline powder. The pure garnet phase of the obtained materials and the contamination from OH groups were studied by the FTIR analysis. Absorption, excitation and emission spectra of LuAG:Pr3+ nano crystalline powder were measured. The effects of heat-treatment temperature on the luminescent properties were investigated. An enhancement of the absorption ratio of 260 nm peak to 213 nm peak with increasing grain size was observed. The quantum efficiency also increased with increasing grain size. It was found that the decay times of the Pr3+ luminescence depends on the grain size and quenching parameter such as OH group. The decay time was increased from 12 nm to 23 nm grain size and then decreased from 23 nm to 31 nm. For a comparison study, Pr3+ doped LuAG powders were also prepared by the co-precipitation method.