Preparation of Sm³⁺–Eu³⁺ coactivating red-emitting phosphors and improvement of their luminescent properties by charge compensation

Abstract

By charge compensating, a series of red-emitting phosphors Ca_0.54Sr_0.16Ca_0.54Sr_0.31Eu_0.08Sm_0.02(MoO₄)_0.6(WO₄)_0.4 were synthesized. Two approaches to charge compensation were used: (a) 2Ca²⁺/Sr²⁺→Eu ³⁺/Sm³⁺+M ⁺, where M⁺ is a monovalent cation like Li⁺, Na⁺ or K⁺; (b) Ca²⁺/Sr²⁺→Eu ³⁺/Sm³⁺+N ⁻, where N⁺ is a monovalent anion like F⁻, Cl⁻, Br⁻, or I⁻. One red LED was made by combining the phosphor and 390–405 nm emitting LED chip under 20 mA forward-bias current, the color purity, chromaticity coordinates and the luminous intensity of which were 99.5%, x=0.66, y=0.33, 5600 mcd, respectively.