Synthesis and photoluminescence enhancement of Ca₃Sr₃(VO₄)₄:Eu³⁺ red phosphors by Sm³⁺ doping for white LEDs

A new type of red-emitting Eu³⁺ and Sm³⁺ co-doped Ca₃Sr₃(VO₄)₄ phosphor was synthesized by the combustion method. The photoluminescence properties and microstructure were investigated by photoluminescence spectroscopy, X-ray powder diffraction, and scanning electron microscopy. All samples were found to match perfectly with the rhombohedral structure and belong to the R3c space group. The photoluminescence emission intensity of the optimal phosphor Ca₃Sr₃(VO₄)₄:0.05Eu³⁺, 0.09Sm³⁺ at 619 nm was significantly enhanced compared with those of Ca₃Sr₃(VO₄)₄:Eu³⁺ samples and commercial Y₂O₃:Eu³⁺ at an excitation wavelength of 393 nm, as a result of the energy transfer from Sm³⁺ to Eu³⁺. The energy transfer process between Sm³⁺ and Eu³⁺ is discussed and interpreted by considering the energy level diagram. Furthermore, the CIE chromaticity coordinate of Ca₃Sr₃(VO₄)₄:0.05Eu³⁺, 0.09Sm³⁺ was closer to the standard red-emitting point (x = 0.67, y = 0.33) than Y₂O₃:Eu³⁺. The luminescence performance of Ca₃Sr₃(VO₄)₄:Eu³⁺, Sm³⁺ upon excitation by near-UV radiation makes it a promising red phosphor for manufacturing white-light-emitting diodes.