The charge transfer transition phenomenon and microstructure of Eu3+-doped NaCaPO4 phosphors sintered with NH4Cl flux via solid-state reaction

NaCa0.95PO4:0.05Eu3+ phosphors with 2 wt.% NH4Cl flux sintered at various sintering temperature (800, 900, 1000, 1100 °C) for 3 h under air atmosphere were synthesized successfully via solid state reaction method. It is found that the addition of NH4Cl flux and different sintering temperatures can affect the morphology and fluorescent properties of NaCa0.95PO4:0.05Eu3+ phosphor. The X-ray diffractions show a single phase and the microstructure observations show uniform morphologies for NaCa0.95PO4:0.05Eu3+ phosphors sintered at the range from 900 °C to 1000 °C, indicating that addition of 2 wt.% NH4Cl flux is helpful for enhancing the crystallization, thus improving the luminescence intensity of the charge transfer transition. The intensity of the excitation peaks displayed a maximum value at 1000 °C. The chromaticity (x, y) is in the orange-red region (0.54, 0.39) and the lifetime value is about 2.1 ms, suitable for the remote phosphor packages.