Improving thermal stability of novel single-component white-light emitting phosphor Ca8MgLu(PO4)(7):Tm3+, Dy-3(+) by back-energy-transfer

The light degradation of WLED devices after long-time use has been proved to be mainly caused by thermal quenching of phosphors, therefore, the design of single-component white-light emitting phosphors with high thermal stability remains a huge challenge. A novel single-phase white light-emitting phosphor Ca8MgLu(PO4)(7):Tm3+, Dy-3(+) was designed and prepared in this work. The photoluminescent results show that white light emission from the phosphor can be achieved by controlling the ratio of Tm3+ and Dy3+ to adjust the relative intensity of the emission at 451 nm of Tm3+ and the emissions at 488, 571 and 660 nm of Dy3+. The luminescence decay results reveal that there is energy transfer from Tm3+ to Dy3+ in Ca8MgLu(PO4)(7):Tm3+,Dy3+ and the efficiency of energy transfer between the two dopants reaches as much as 55%. Temperature-dependent luminescent analyses suggest the highly stable emission of Ca8MgLu0.76(PO4)(7):0.12Tm(3+),0.12Dy(3+) as the integrated emission intensity of the phosphor at 475 K reduces only about 13% of that at room temperature, which is due to the back-energy-transfer from highly doped Dy3+ to Tm3+ that compensates the luminescence energy. This single-phase white-light emitting phosphor exhibits superior color and luminescence stability and thus may find a potential application in WLEDs.