High-efficiency energy transfer in the strong orange-red-emitting phosphor CeO₂:Sm³⁺, Eu³

High-efficiency energy transfer (ET) from Sm³⁺ to Eu³⁺ leads to dominant red emission in Sm³⁺, Eu³⁺ co-doped single-phase cubic CeO₂ phosphors. In this work, a series of Sm³⁺ singly and Sm³⁺/Eu³⁺ co-doped CeO₂ cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at 800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm excitation, the Sm³⁺ singly doped CeO₂ phosphor emitted strong yellow-red light at 573 nm (⁴G_5/2-⁶H_5/2) and 615 nm (⁴G_5/2-⁶H_7/2). Meanwhile, the CeO₂:Sm³⁺, Eu³⁺ phosphors showed the emission characteristic of both Sm³⁺ and Eu³⁺, with the highest emission intensity at 631 nm. The emission intensity of Sm³⁺ decreased with increasing Eu³⁺ content, suggesting the ET from Sm³⁺ to Eu³⁺ in the CeO₂:Sm³⁺, Eu³⁺ phosphors. The decay kinetics of the ⁴G_5/2-⁶H_5/2 transition of Sm³⁺ in the CeO₂:Sm³⁺, Eu³⁺ phosphors were investigated, confirming the high-efficiency ET from Sm³⁺ to Eu³⁺ (reached 84%). The critical distance of energy transfer (R_C = 13.7 Å) and the Dexter theory analysis confirmed the ET mechanism corresponding to the quadrupole-quadrupole interaction. These results indicate that the high-efficiency ET from Sm³⁺ to Eu³⁺ in CeO₂:Sm³⁺, Eu³⁺ phosphors is an excellent strategy to improve the emission efficiency of Eu³⁺.