Ba3LaNa(PO4)3F:Tm3+, Dy3+: A tunable blue-white color emitting phosphor via energy transfer for UV white LEDs

A series of Tm³⁺/Dy³⁺ co-doped Ba₃LaNa(PO₄)₃F (BLNPF) phosphors were synthesized successfully via a high-temperature solid-reaction, and luminescence properties were investigated. Upon near violet excitation, BLNPF:Tm³⁺, Dy³⁺ phosphors exhibit Tm³⁺:¹D₂-³F₄ and Dy³⁺:⁴F_9/2-⁶H_J (J = 15/2, 13/2, 11/2) transitions with different luminescence intensity. The emitting color of the obtained products was found to shift from blue to white as a result of efficient energy transfer (ET) from Tm³⁺ to Dy³⁺ ions. According to photoluminescence emission intensity, the positive effect of activator on ETefficiency was calculated and the maximum ET efficiency was found around 72.6% with Dy³⁺ concentration was 0.04. By means of Dexter’s theoretical model, furthermore, dipole-dipole interaction was confirmed as the mechanism of energy transfer from Tm³⁺ to Dy³⁺ ions. The results suggested that BLNPF:Tm³⁺, Dy³⁺ phosphor might be a promising single-phased white-light-emitting phosphor for UV white-light LED.