Temperature sensing performance of Er3+:Yb3+ co-doped CaF2 ceramic powders using near-infrared light

Abstract

Luminescent materials for application in temperature sensing have caught a lot of interest in recent years. Particularly erbium (Er3+)-doped fluoride-based materials (EFM), which are readily accessible by near-infrared (NIR) excitation to produce efficient photon conversion. It has been established that ytterbium (Yb3+) may improve the performance of EFMs in both bulk and nanostructured forms by energy transfer channels among rare-earth ions in interstitial clusters. In this work, a comprehensive analysis of the Er3+:Yb3+:CaF2 crystalline structure, photoluminescence, and energy transfer from Yb3+ to Er3+ is presented for powders prepared by combustion synthesis. The Er3+:Yb3+:CaF2 powders display exceptional photon down-shift and up-conversion when exposed to NIR light (λ = 975 nm). The luminescence spectral change of the NIR emission around 1.5 μm, which corresponds to the Er3+ electronic transition 4I13/2 → 4I15/2, was investigated in a temperature range of 298–423 K for application in temperature sensing of biological systems exploring the third biological window. The luminescence intensity ratio technique was applied to the thermally coupled Stark sublevels of states 4I13/2 and 4I15/2 with the highest estimated temperature relative sensitivity being around 0.4 %/K at 298 K.