Highly efficient red-emitting Ca₂YSbO₆:Eu³⁺ double perovskite phosphors for warm WLEDs

Highly efficient red-emitting Eu³⁺-doped double perovskite Ca₂YSbO₆ phosphors have been successfully prepared by the traditional high-temperature solid state method. The phase purity, photoluminescence and decay properties as a function of the Eu³⁺ concentration have been investigated in detail. The XRD results demonstrate that all of the obtained phosphors can be assigned to a pure monoclinic structure. Upon 464 nm excitation, a strong red emission situated at 614 nm (⁵D₀-⁷F₂) indicates that Eu³⁺ ions occupy a site with low symmetry. The quenching concentration of Eu³⁺ ions reaches as high as 70 mol% and the quenching mechanism is discussed. Especially, the prepared phosphor exhibits a high quantum efficiency of 92.1% and superior thermal stability, with PL intensity at 423 K up to 81.6% of that at room temperature. Moreover, a warm white light with a correlated color temperature of 4720 K and a color rendering index of 82.6 is achieved by fabricating a Ca₂YSbO₆:Eu³⁺ phosphor in a 460 nm blue-InGaN chip together with the commercial Y₃Al₅O₁₂:Ce³⁺ yellow phosphor.