Blue emission properties of Eu-doped CaAl2O4 phosphors synthesized by a flux method

The effects of the firing conditions, a flux, and doping concentrations on the phase transformations of CaO–Al2O3–Eu2O3 systems and luminescent properties were investigated. Depending on the amount of H3BO3 and firing conditions, three phases of Ca12Al14O33, CaAl2O4, and CaAl4O7 were observed. Both Ca12Al14O33 and CaAl4O7 phases did not contributed to the emissions. A single phase CaAl2O4 showed a blue emission at 440 nm with 330 nm excitation. Europium concentrations more than 6 mol% exceeded the solubility for Ca1−xEuxAl2O4 solid solution. The excess Eu contributed to the formation of the EuCaAl3O7 phase, resulting in the decrease and the red-shift in photoluminescence.