Strong energy transfer and color tunable emission in Eu2+ and Mn2+ co-doped Na2BaSr(PO4)2 phosphor

The new dual-emitting and color tunable single phase of Na2BaSr(PO4)2:0.03Eu2+, xMn2+ (NBSP:0.03Eu2+, xMn2+) phosphor are successful prepared in this work. The phase purity and photoluminescence properties are investigated. Regarding to the coordination, valence and cation radius, the Eu2+ ions occupy the Sr2 and Sr3 site and Mn2+ ions occupy the Sr3 site. According to the photoluminescence (PL) spectra of NBSP:0.03Eu2+, xMn2+ (x = 0–0.09), the strong energy transfer (ET) between Eu2+ and Mn2+ exists in these phosphors. The strong ET efficiency from Eu2+ to Mn2+ is as high as 92%, while the ET mechanism of Eu2+ and Mn2+ is quadrupole-quadrupole interaction. Moreover, the CIE coordinate of Eu2+ and Mn2+ co-doped Na2BaSr(PO4)2 phosphors can realize the color tunable emission from blue to cold white. The temperature dependent photoluminescence intensity of NBSP:0.03Eu2+, 0.05Mn2+ phosphor still keeps 75.8% of that initial intensity when the temperature is 150 °C. In summary, the NBSP:0.03Eu2+, xMn2+ phosphors have a promising application in white light LED.