Energy transfer, multi-colour emission and high thermal stability behaviour of K2Tb1−xEuxHf(PO4)3 with langbeinite-type structure. Issue 29 (9th July 2020) - Zhao, Dan
Abstract : This study provides a new series of solid solution phosphors, K2 Tb1− x Eu x Hf(PO4 )3, with multi-color emission evolution and high thermal stability for LED lamps. Abstract : Eu 3+ /Tb 3+ codoped phosphors usually present multi-color emitting performances ranging from green and yellow to red, which not only have theoretical but also practical significance. In this work, we prepared a new langbeinite-type compound, K2 TbHf(PO4 )3, determined its structure via single-crystal X-ray diffraction, and prepared solid solutions of K2 Tb1− x Eu x Hf(PO4 )3 ( x = 0–1) with multi-color emitting properties. The structure of the solid solutions was refined by the Rietveld method, showing a constant lattice structure with a change in Eu 3+ concentration from 0 to 100%. For the typical sample, K2 Tb0.99 Eu0.01 Hf(PO4 )3, both Tb 3+ and Eu 3+ emission peaks were observed upon excitation by near ultraviolet light of 378 nm, whereas only the characteristic peaks of Eu 3+ were observed when the excitation source was 393 nm. This suggests that the energy transfer from Tb 3+ to Eu 3+ occurred, but not the reverse transfer. The emitting color of K2 Tb1− x Eu x Hf(PO4 )3 could change from green and yellow to red by simply modulating the concentration of Eu 3+ . Meanwhile, the temperature-dependent analysis proved the high thermal stability of the prepared phosphor. Finally, green, yellow, and red near-ultraviolet pumped LEDs were fabricated using three typical phosphors with x = 0, 0.005, and 0.10, respectively.