Investigations on the luminescence of emission-tunable Ca10K(PO4)7:Eu2+, Sr2+, Mg2+ phosphors for white LEDs

Abstract

Ca₁₀K(PO₄)₇:Eu²⁺, Sr²⁺, Mg²⁺ (CKP:Eu²⁺, Sr²⁺, Mg²⁺) phosphors were prepared by the solid-state reaction method, and their photoluminescence properties under near-ultraviolet excitation were studied. By measuring the diffuse reflection spectrum, the optical bandgap of the CKP host was determined to be about 5.39 eV. Eu²⁺-activated CKP shows an asymmetrical emission band in the range of 425–650 nm, derived from various Eu²⁺ emission centers. The corresponding excitation spectrum presents a broad excitation band which can match well with the emission wavelength of the near ultraviolet LED chip. By introducing Sr²⁺ and Mg²⁺ into CKP:Eu²⁺, tunable emission has been realized from light blue to greenish yellow including white, which is mainly owing to the effect of Sr²⁺ and Mg²⁺ on the structure of CKP. The above investigation results indicate the CKP:Eu²⁺, Sr²⁺, Mg²⁺ phosphors have potential applications in white LEDs.