Development of NaCaLa(MoO4)3:Sm3+ orange-red emitting phosphors with high color purity and thermal stability

Abstract

A series of NaCaLa(MoO₄)₃:Sm³⁺ orange-red phosphors were synthesized via conventional solid-state reaction technique and their phase purity, luminescence characteristics, and thermal stability were investigated in detail. Under excitation at 405 nm, NaCaLa(MoO₄)₃:Sm³⁺ phosphors exhibit several emissions around the orange-red region, with an intense peak at 645 nm arising from the electric dipole transition of Sm³⁺, which is significantly enhanced by the asymmetric local environment. The optimum Sm³⁺ concentration for NaCaLa_1-x(MoO₄)₃:xSm³⁺ phosphor was determined to be 6 %. The optimized NaCaLa_0.94(MoO₄)₃:0.06Sm³⁺ phosphor shows a color purity of 98.7 % and an internal quantum efficiency (IQE) of 38.04 %. Furthermore, at a temperature of 150 °C, the NaCaLa_0.94(MoO₄)₃:0.06Sm³⁺ retained 91.47 % of its room-temperature emission intensity, demonstrating remarkable thermal stability. Based on the results, the strong 645 nm emission under nUV excitation highlights their potential for red phosphors in phosphor-converted WLEDs.