Defective band enhance the single green upconversion luminescence of Ca9Y(VO4)7: Yb3+/Er3+ phosphors by doping with Ba2+ ions

The present work investigates the near-single green emission properties of Ba 2+ doped Ca 9 Y(VO 4 ) 7 : Yb 3+ /Er 3+ upconversion luminescence. The Ba 2+ doped Ca 9 Y(VO 4 ) 7 : Yb 3+ /Er 3+ phosphors were successfully synthesized via the high-temperature solid-phase method. XRD pattern analysis showed that Ca 9 Y(VO 4 ) 7 : Yb 3+ /Er 3+ /Ba 2+ was a single phase, and Ba 2+ doping did not induce heterophase phase. Under 980 nm near-infrared laser irradiation, Ca 9 Y(VO 4 ) 7 : Yb 3+ /Er 3+ /Ba 2+ phosphors emit strong green luminescence (530 nm, 2 H 11/2 → 4 I 15/2 , 557 nm, 4 S 3/2 → 4 I 15/2 ) and weak red luminescence (664 nm, 4 F 9/2 → 4 I 15/2 ). The upconversion green-red luminescence integral intensity ratio of Ca 9 Y(VO 4 ) 7 : Yb 3+ /Er 3+ /Ba 2+ phosphor is 32.1. This enhancement can be attributed to the presence of defect bands that facilitate excitation photon absorption and efficient energy transfer from abundant electrons into Yb 3+ ( 2 F 5/2 ) and Er 3+ ( 4 I 11/2 ) ions. More importantly, the maximum S A and S R of Ca 9 Y(VO 4 ) 7 : Yb 3+ /Er 3+ /Ba 2+ phosphor as a temperature sensor are 1.44 % K −1 (at 548 K) and 1.28 % K −1 (at 298 K), respectively.