Preparation and strong green upconversion luminescence of Ca₉Y(VO₄)₇: Yb³⁺/Er³⁺ phosphor

Exploring novel oxysalt compounds remains significant due to their affordability and versatile applications, such as serving as laser crystals, piezoelectric crystals, frequency-doubling crystals, and luminescent materials. Specifically, this study introduces a new near-single green upconversion luminescent Ca-9(VO4)(7): Yb3+/Er3+ material, synthesized through high-temperature solid-phase methods. When subjected to 980 nm near-infrared laser irradiation, the Ca-9(VO4)(7): 0.3 Yb3+, 0.02 Er3+ phosphor demonstrates robust green luminescence at 531 nm (H-2(11/2) -> I-4(15/2)) and 558 nm (S-4(3/2) -> I-4(15/2)), accompanied by faint red luminescence at 665 nm (F-4(9/2) -> I-4(15/2)). The optimal doping concentrations for Yb3+ and Er3+ ions, yielding the highest upconversion luminescence intensity, are determined to be 0.3 and 0.02, respectively. The investigation elucidates the upconversion luminescence mechanism through the downward shift spectrum in photoluminescence and the pumping power dependence of upconversion green-red luminescence. The primary excitation pathway identified for the upconversion process in Ca9Y(VO4)(7): 0.3 Yb3+, 0.02 Er3+ involves Yb3+ (F-2(5/2)) + Er3+ (I-4(11/2)) -> Yb3+ (F-2(7/2)) + Er3+ (F-4(7/2)). This research contributes to the exploration of new materials, injecting vitality into modern industries and production processes.