Characterization and optical properties of (Gd1−x, Prx)2O2S nano-phosphors synthesized using a novel co-precipitation method

A novel co-precipitation method for synthesizing (Gd1−x, Prx)2O2S nano-phosphors was developed, using the commercially available Gd2O3, Pr6O11, H2SO4 and NaOH as the starting materials. This method has the advantage of controllable phosphor particle size and shape, simplicity in processing, low cost, and not involving toxic carbon disulfide or hydrogen sulfide. It was found that the as-synthesized precursor is mainly composed of (Gd1−x, Prx)2(OH)4SO4·nH2O. By calcining the (Gd1−x, Prx)2(OH)4SO4·nH2O precursor at a temperature higher than 700 °C for 1 h in flowing hydrogen, pure quasi-spherical shaped (Gd1−x, Prx)2O2S particles can be synthesized. The (Gd1−x, Prx)2O2S particles have a narrow size distribution with a mean grain size of about 20-30 nm. UV-vis spectra indicates that the absorption edge of the samples has a blue shift with increasing calcination temperature, while PL spectra of (Gd1−x, Prx)2O2S under 301 nm excitation show a green emission at 511 nm as the most prominent peak, which corresponds to the 3P0 → 3H4 transition of Pr3+ ions. The optimal x value is 0.01 for the highest luminescent emission intensity.