Color tunable phosphor CaMoO4:Eu3+,Li+ via energy transfer of MoO42−–Eu3+ dependent on morphology and doping concentration

The cooling rate and the solubility of molybdate in molten salt play crucial roles on the microscopic morphologies and photoluminescence (PL) properties of the phosphor CaMoO4:Eu3+,Li+. Undoped CaMoO4 exhibits self-activated green PL with a broad emission band which is assigned to the spin forbidden 3T1,2–1A1 transition of the MoO42− complex. The strong UV absorption of undoped CaMoO4 is originated from the charge transfer from O2− ligands to the central Mo6+ ions inside MoO42− group. The emission of the phosphor CaMoO4:Eu3+,Li+ obtained by molten salt synthesis (MSS) at 900 °C is composed of a broad green emission from MoO42− and a group of sharp red emission peaks from f–f transitions of Eu3+. Efficient energy transfer from MoO42− to Eu3+ is responsible for the increased red PL of the phosphor. The dependence of energy transfer efficiency on the processing conditions and doping concentration has been investigated.