Synthesis and luminescence properties of BaWO4:Sm3+, Mo6+/K+ red phosphor
BaWO 4 :Sm 3+ , Mo 6+ /K + phosphors are synthesized by a high temperature solid-state reaction method in air. The very strong emission bands peaking at ~600 and 644 nm and the strongest excitation band peaking at ~403 nm are assigned to the 4 G 5/2 → 6 H J (J = 7/2 and 9/2) and 6 H 5 / 2 → 4 F 7 / 2 transitions of Sm 3+ ion, respectively. The optimal Sm 3+ doping concentration is ~5 mol%. Emission intensity of BaWO 4 :Sm 3+ phosphor is increased more than twice owing to charge compensation when the K + ion is codoped as charge compensator, however, Mo 6+ ions is small influence to its emission intensity. The energy transfers and luminous mechanism are explained by using energy level diagrams of WO 4 2− group and Sm 3+ ion. Lifetimes of Ba 0.925 WO 4 :0.05Sm 3+ , Ba 0.925 W 0.9 Mo 0.1 O 4 :0.05Sm 3+ , and Ba 0.9 K 0.05 WO 4 :0.05Sm 3+ phosphors with excitation 403 nm are about 0.933, 0.882, and 0.693 ms, respectively. The experiment results indicate that BaWO 4 :Sm 3+ , Mo 6+ /K + phosphors will be a potential red phosphor candidate for white LEDs based on near UV (~403 nm) LED chip and research contents are useful to improve luminescence properties of Sm 3+ -doped phosphors.
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