Hydrothermal syntheses and photoluminescence properties of rare-earth tungstate as near ultraviolet type red phosphors

Abstract

Three families of scheelite CaWO₄-based red luminescent phosphors, Ca_1−1.5xWO₄:xEu³⁺ (0.02 ≤ x ≤ 0.09), Ca_0.925−ySr_yWO₄:0.05Eu³⁺ (0 ≤ y ≤ 0.9) and Ca_0.625Sr_0.30W_1−zMo_zO₄:0.05Eu³⁺ (0 ≤ z ≤ 0.7) were hydrothermally prepared and characterized. The substitutions of Sr²⁺ for Ca²⁺ and Mo⁶⁺ for W⁶⁺, which improve local symmetries surrounding Eu³⁺, assisted the energy transfer from O²⁻ to Eu³⁺ in the process of optimizing the luminescence properties. The z = 0.2 members of Ca_0.625Sr_0.30W_0.80Mo_0.20O₄:0.05Eu³⁺ exhibited excellent bright red luminescence at 616 nm under near-UV excitation, narrowed emission spectra, room temperature luminescence lifetimes of milliseconds and maximum quantum efficiencies of 49%.