Improving upconversion luminescence intensity of BiTa 7 O 19 :Er 3+ /Yb 3+ by polyvalent Sb co-doping.

BiTa 7 O 19 :Er 3+ /Yb 3+ /Sb phosphors were successfully synthesized by high temperature solid sintering. X-ray diffraction (XRD), fluorescence spectrometry and X-ray photoelectron spectroscopy (XPS), were used to analyze the phase structure, upconversion luminescence (UCL) features and Sb valence state, respectively. The results suggest that polyvalent Sb with Sb 3+ and Sb 5+ can replace the Ta 5+ sites in a BiTa 7 O 19 host to form a pure phase. Compared with BiTa 7 O 19 :0.1Er 3+ /0.4Yb 3+ , polyvalent Sb doping further improves UCL intensity by 1.2 times under 980 nm laser stimulation with a powder density of 44.59 W cm -2 . This is due to the adjustment of the local lattice structure of BiTa 7 O 19 by the polyvalent Sb. The maximum absolute sensitivity ( S A ) and relative sensitivity ( S R ) can be estimated from the UCL variable-temperature spectra as 0.0098 K -1 at 356 K and 0.0078 K -1 at 303 K using the luminescence intensity ratio (LIR) approach. The outcomes show that host local lattice adjustment using polyvalent elements is an effective way to improve luminescence intensity, and it is possible to use BiTa 7 O 19 :Er 3+ /Yb 3+ /Sb as a temperature sensor.