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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.
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