NaLaMgWO₆:Pr³⁺: A novel blue-light excitable red-emitting phosphor for white light-emitting diodes

A series of Pr³⁺-doped double perovskite tungstate NaLaMgWO₆ with composition NaLa_1−xMgWO₆:xPr³⁺ (x = 0.01–0.15) were synthesized by a conventional solid-state reaction technique at high temperature. The crystal structure, microstructure, photoluminescence properties as well as decay curves are investigated systematically. The excitation spectrum consists of a host-related excitation band (250–350 nm) and some f-f transition bands of Pr³⁺ (440–500 nm), in which the latter ones can match well with the commercially available blue-emitting LED chip. Upon excitation with UV (~ 268 nm) and blue light (~ 451 nm), the as-prepared phosphors exhibit red emission originating in the transitions from ³P₀ state of Pr³⁺, in which the transition of ³P₀ → ³F₂ (~ 654 nm) is dominant. The optimal concentration of Pr³⁺ is confirmed to be 7%, beyond which the d-d interaction plays an important role in the concentration quenching phenomenon of Pr³⁺. Furthermore, the luminescence decay lifetime for ³P₀ → ³F₂ transition of Pr³⁺ is of microsecond level and decreases with the increase in Pr³⁺ ion concentration. Finally, a white LED device is fabricated with the combination of phosphors (YAG:Ce³⁺+NaLaMgWO₆:Pr³⁺) and commercial blue-emitting LED chip to explore preliminarily the potential application of NaLaMgWO₆:Pr³⁺ red phosphor in solid state lighting field.