Warm white light emission, thermochromic property and long persistent luminescence derived from multi-sites of Eu2+/Eu3+ in host lattice

Making a further insight into the structure-property relation of luminescent materials is not only in theory but also with reference value in developing more practical materials in this field. This paper reports a new luminescent material K5Y(P2O7)2:Eu (KYP:Eu), in which the Eu2+ dopants may occupy K+ or Y3+ sites. As a result, a warm white emission covering a wide range of 430–720 nm is generated at room temperature, in which the bands at 430–520 nm are due to Eu2+ in K+ sites and the bands at 530–720 nm are attributed to Eu2+ in Y3+ sites. Owing to the difference of Eu2+ sensitivity at different sites, or the effects of co-existence of Eu2+ and Eu3+, a position interchange between Eu2+ and Eu3+ happens at very low temperature (<175 K), which leads to the emission colors turning from dark blue, through blue-white and finally to white with increasing temperature from 10 to 450 K. Besides, the phosphor KYP:Eu shows long-persistent luminescence (LPL), which could be improved after doping 0.5% Pr3+. These results suggest that prepared phosphor has utilization potentiality in multiple fields of white light-emitting diodes (WLEDs), optical thermometry and persistent luminescence.