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 Ba2+ doped Ca9Y(VO4)7: Yb3+/Er3+ upconversion luminescence. The Ba2+ doped Ca9Y(VO4)7: Yb3+/Er3+ phosphors were successfully synthesized via the high-temperature solid-phase method. XRD pattern analysis showed that Ca9Y(VO4)7: Yb3+/Er3+/Ba2+ was a single phase, and Ba2+ doping did not induce heterophase phase. Under 980 nm near-infrared laser irradiation, Ca9Y(VO4)7: Yb3+/Er3+/Ba2+ phosphors emit strong green luminescence (530 nm, 2H11/2 -> 4I15/2, 557 nm, 4S3/2 -> 4I15/2) and weak red luminescence (664 nm, 4F9/2 -> 4I15/2). The upconversion green-red luminescence integral intensity ratio of Ca9Y(VO4)7: Yb3+/Er3+/Ba2+ 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 Yb3+ (2F5/2) and Er3+ (4I11/2) ions. More importantly, the maximum SA and SR of Ca9Y(VO4)7: Yb3+/Er3+/Ba2+ phosphor as a temperature sensor are 1.44 % K 1 (at 548 K) and 1.28 % K-1 (at 298 K), respectively.