Effect of doping concentration and sintering temperature on structure and photoluminescence properties of blue/red emitting bi-phase Eu3+/Eu2+-doped Sr5(PO4)3Cl/Sr3(PO4)2phosphors

Blue/red emitting bi-phase Eu3+/Eu2+-doped SrPCl-based phosphors were synthesized using a co-precipitation method followed by sintering process in air ambient and in reducing gas. The effect of sintering/reducing temperature and Eu concentration on the structure, morphology and luminescent spectra were investigated. XRD patterns analysis showed that the phosphors contain bi-phase of Sr5(PO4)3Cl and Sr3(PO4)2 due to the decomposition of Cl atoms at high sintering temperature. The decomposition, however, could be prevented by high Eu doping content. The optimum PL performances are obtained for the phosphor sintering/reducing at 1000 °C and with Eu doping concentration of 5.5%. The relative intensity of the red and blue emission from the bi-phase Sr5(PO4)3Cl/Sr3(PO4)2 phosphor could be controlled by controlling the reducing temperature. At low reducing temperatures of 400 to 650 °C, dual red and blue emission Eu3+/Eu2+ bi-phase SrPCl phosphor can be achieved. Being stable and can be well excited by UV excitation source, the blue/red emitting bi-phase Eu3+/Eu2+-doped SrPCl-based phosphor is a potential candidate for plant growth LEDs.