Energy transfer, multi-colour emission and high thermal stability behaviour of K2Tb1-xEuxHf(PO4)3 with langbeinite-type structure

Eu3+/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, K2TbHf(PO4)(3), determined its structureviasingle-crystal X-ray diffraction, and prepared solid solutions of K2Tb1-xEuxHf(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, K2Tb0.99Eu0.01Hf(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 K2Tb1-xEuxHf(PO4)(3)could change from green and yellow to red by simply modulating the concentration of Eu3+. 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 withx= 0, 0.005, and 0.10, respectively.