Single-band red up-conversion emission of Er3+ doped Yb0.2Zr0.8O1.9 phosphors and multi-mode optical temperature sensing

• Single-band red UC emission was obtained in Yb 0.2 Zr 0.8 O 1.9 : Er 3+ under 980 and 1550 nm excitations. • Dependence of UC luminescence properties on Er 3+ concentrations were discussed upon 980 and 1550 nm excitations. • Multi-mode temperature sensing behavior was studied via FIR technology using TCELs and NTCELs excited at 980 nm. This work used a solid-state technique to produce a variety of Er 3+ -doped Yb 0.2 Zr 0.8 O 1.9 (Yb 0.2 Zr 0.8 O 1.9 : Er 3+ ) phosphors. The temperature sensing characteristics and up-conversion luminescence (UCL) properties of Er 3+ in Yb 0.2 Zr 0.8 O 1.9 : Er 3+ phosphors under 980 and 1550 nm excitations were investigated. A virtually pure red UC emission was obtained with a spectral color purity of 95.65 % and 99.92 % when excited at 980 and 1550 nm, respectively. Based upon the fluorescence intensity ratios of temperature-dependent distinct emissions, the temperature sensing capabilities of the materials were investigated. The relative sensitivity ( S R ) generated from the red emission reaches 0.74 % K −1 at 298 K, whereas the one derived from the green emission attains its highest value of 1.51 % K −1 at 688 K utilizing the thermally coupled energy levels (TCELs). At 495 K, the S R for non-thermally coupled energy levels (NTCELs) reaches its highest value of 0.46 % K −1 . This study reveals that Yb 0.2 Zr 0.8 O 1.9 : Er 3+ is an excellent red UC phosphor and has potential applications in three-dimensional display and temperature sensing.