Synthesis and luminescence enhancement of CaY_0.6(MoO₄)_1.9:Eu³⁺ red phosphors by Sm³⁺ co-doping

Eu³⁺ activated red phosphors based on the CaY_x(MoO₄)_1.5x+1 (x = 0.2, 0.4, 0.6, 1, 2) as host materials were synthesized by using a combustion method. XRD analysis demonstrated that the synthesized samples matched with the standard card CaMoO₄ (JCPDS NO.77-2239) belonging to the tetragonal of the I4₁/a space group. All samples showed several narrow sharp emission peaks under 393 nm n-UV excitation, the strongest of which was at 618 nm attributed to the ⁵D₀→⁷F₂ transition of Eu³⁺. The optimal composition of the host was found to be CaY_0.6(MoO₄)_1.9 (hereafter referred to as CYMO). After doping Sm³⁺ into CYMO:Eu³⁺ phosphor, the absorption peaks of Eu³⁺ at 393 and 464 nm were broadened, and the peak intensity was also significantly higher than that of single-doped Eu³⁺. The energy transfer phenomenon between Sm³⁺ and Eu³⁺ was discovered by the excitation and emission spectra in CYMO:Eu³⁺,Sm³⁺ phosphors, and verified by the fluorescence lifetime of Sm³⁺ ions in the phosphors. The energy transfer mechanism between Sm³⁺ and Eu³⁺ is a dipole-dipole interaction, where the energy transfer efficiency in CYMO phosphor doped with 13% Eu³⁺ and 3% Sm³⁺ is 17.9%. The CIE coordinate and color purity were calculated as (x = 0.6598, y = 0.3388) and 93.72%, which indicated that the CYMO:13%Eu³⁺,3%Sm³⁺ phosphor is a red phosphor with excellent performance for potential application in n-UV light excited w-LEDs.