Highly Eu³⁺ ions doped novel red emission solid solution phosphors Ca₁₈Li₃(Bi,Eu)(PO₄)₁₄: structure design, characteristic luminescence and abnormal thermal quenching behavior investigation

To research and develop potential phosphors for ultraviolet-based white light emitting diodes, a novel red emission phosphate phosphor Ca₁₈Li₃Bi_1-xEu_x(PO₄)₁₄ was synthesized and investigated in the full range of 0 ≤x≤ 1. The phase purity and crystal structure of the solid solution phosphors were investigated in detail by employing X-ray diffractometer structure refinement, scanning electron microscopy and energy dispersive spectrometry. The crystal structure information was confirmed and the structure as well as the doping concentration dependent characteristic photoluminescence properties were discussed in detail. The results indicated that high Eu³⁺ doping content x could be realized in Ca₁₈Li₃Bi_1-xEu_x(PO₄)₁₄ solid solutions even when x = 1. The luminescence performance revealed that Ca₁₈Li₃Bi_1-xEu_x(PO₄)₁₄ phosphors could emit intense red emission under 394 nm excitation with excellent CIE chromaticity coordinates and high color purity. The concentration dependent emission decay behavior at room temperature and the temperature dependent decay behavior were studied to investigate the luminescent dynamics. The abnormal thermal quenching behavior was investigated via the temperature dependent emission. The related mechanism was discussed through thermoluminescence analysis, charge compensation contrast test and the cooling emission curve measurement, and the thermal activation energy was studied. The above results indicated that the Ca₁₈Li₃Bi_1-xEu_x(PO₄)₁₄ could be a promising red-emitting phosphor for white light emitting diodes.