An up-conversion Ba3In(PO4)3:Er3+/Yb3+ phosphor that enables multi-mode temperature measurements and wide-gamut ‘temperature mapping’

Abstract

At present, most fluorescent materials that can be used for optical temperature measurement exhibit poor thermochromic performance, which limits their applications. In this study, the phosphor Ba₃In(PO₄)₃:Er/Yb was synthesized with a high doping concentration of Yb³⁺, and it emitted composition- and temperature-induced wide color gamut up-conversion luminescence from red to green. Four modes of fluorescence thermometry can be realized in the temperature range of 303–603 K, which is based on the ratio of fluorescence intensity between thermally coupled energy levels and non-thermally coupled energy levels, color coordinate shift, and fluorescence decay lifetime, respectively. The highest Sr value obtained was 0.977% K⁻¹. Taking advantage of the fact that temperature can significantly change the luminous color of the phosphor Ba₃In(PO₄)₃:0.02Er³⁺/0.05Yb³⁺, we demonstrated ‘temperature mapping’ on a smooth metal surface with multiple optical encryptions. These results indicate that the Ba₃In(PO₄)₃:Er/Yb phosphor is an excellent fluorescent material for thermal imaging and has great application potential in temperature visualization measurement and optical encryption.