Cationic substitution induced tuning of photoluminescence in Ba_2.94-2xLa_xNa_xP₄O₁₃: 0.06Eu phosphors for WLEDs

The cationic substitution of [La³⁺-Na⁺] for [Ba²⁺-Ba²⁺] pairs in the Eu²⁺ doped Ba₃P₄O₁₃ (BPO) phosphors is designed to investigate the effect on Eu valence state and photoluminescence properties. Energy dispersive spectroscopy (EDS) analysis demonstrates the successful incorporation of La³⁺ and Na⁺ into BPO, forming Ba_2.94-2xLa_xNa_xP₄O₁₃ (BLNPO). Eu³⁺ ions doped in BLNPO host can only be partly reduced to Eu²⁺ state under a reducing atmosphere and the reduction mechanism is proposed. BLNPO: Eu exhibits a blue-green broad emission band derived from Eu²⁺ and a series of sharp emission lines from 570 to 720 nm assigned to the electron transition of ⁵D₀→⁷F_J (J = 0, 1, 2, 3, 4) of Eu³⁺. The emission colors of the BLNPO: Eu phosphors can be tuned from blue-green to white and eventually to orange via regulating [La³⁺-Na⁺] content. Through this strategy, color-tunable white light emission is successfully achieved and optimized in single-phase BLNPO host, which enables the BLNPO: Eu phosphors to be potential color-tunable phosphor candidates for WLEDs.