Synthesis of new green emitting phosphors based on rare earth oxycarbonates

New green emitting phosphors, hexagonal II-type Gd2O2CO3:Tb3+ and Y2O2CO3:Tb3+, were synthesized by the simple flux method and their luminescence properties were compared with that of II-La2O2CO3:Tb3+. Bright green emission was observed in each sample and their particle sizes were in submicron scale. The excitation spectrum consisted of a broad band and some sharp peaks, which were corresponding to the 4f–5d transition of Tb3+ and 4f–4f transition of Gd3+ and Tb3+, respectively. The excitation wavelength of the 4f–5d bands depends on the distance between Tb3+ and O2−, which affects the crystal field effect on the 5d levels of Tb3+. Among lanthanum, gadolinium, and yttrium oxycarbonates, Gd2O2CO3 is the most suitable host to obtain high emission intensity and the maximum intensity was obtained at the composition of Gd2O2CO3:17 at.% Tb3+, where it was 101% of that of a commercial LaPO4:Ce3+,Tb3+ phosphor.