Tunable photoluminescence properties of Eu(II)- and Sm(III)-coactivated Ca_9Y(PO_4)_7 and energy transfer between Eu(II) and Sm(III)

A single-phased tunable color conversion phosphor for WLED was prepared by coactivating Ca9Y(PO4)7 with Eu2+ and Sm3+ ions. The structure, UV-visible and photoluminescence spectra of the phosphor were studied as a function of annealing atmosphere and concentration ratio of Eu2+/Sm3+. The coexistence of Eu2+ and Sm3+ was achieved by annealing the phosphor in a reducing atmosphere. The as-obtained phosphors showed a blended emission of blue-green and orange-red light upon near-UV excitation. White light emission was realized by adjusting the concentration ratio. Energy transfer and dominant interaction between Eu2+ and Sm3+ was also studied.