Extremely intense pure green upconversion luminescence in Ho3+/Yb3+ co-doped BiTa7O19 phosphors under 980 nm laser excitation

A series of BiTa 7 O 19 (BTO):Ho 3+ /Yb 3+ phosphors were prepared by high-temperature solid state sintering, which exhibited outstanding pure green upconversion luminescence (UCL) under 980 nm laser excitation. When Ho 3+ doping 10 mol%, Yb 3+ has almost no concentration quenching point. By optimizing the preparation process, the phase purity of the sample can be improved. Under 980 nm laser excitation power density of 124.99 W/cm 2 , the UCL intensity of the optimized sample is 1.79 times that of the non-optimized sample. The maximum relative temperature sensitivity S R of 0.384% K −1 at 557 K and 0.40% K −1 at 723 K can be obtained by using luminescence intensity ratio (LIR) technique. All experiments show that BTO is an excellent UCL host, and BTO:Ho 3+ /Yb 3+ can be used in UCL display and temperature sensing.