Energy transfer and luminescent properties of Ca8MgLu(PO4)7:Tb3+/Eu3+ as a green-to-red color tunable phosphor under NUV excitation

Abstract

Two series of single-composition Ca₈MgLu(PO₄)₇:Tb³⁺ and Ca₈MgTb(PO₄)₇:Eu³⁺ phosphors were prepared by a high-temperature solid-state reaction technique, and their phase structures were characterized by powder X-ray diffraction (XRD). The excitation and emission spectra, and fluorescence decays were measured and discussed in detail. The results reveal that Tb³⁺ can efficiently transfer excitation energy to Eu³⁺ via its 4f states and therefore sensitizes Eu³⁺ emission under NUV excitation. By adjusting the ratio of Eu³⁺ and Tb³⁺, we can tune the emission color of Ca₈MgTb(PO₄)₇:Eu³⁺ from green to yellow, orange and pure red. For Ca₈MgTb_0.1(PO₄)₇:0.9Eu³⁺, the emission intensity at 150 °C is 87.44% of that at 25 °C, which makes it be a potential pure red phosphor for NUV LEDs.