Spectral-Kinetic Characterization of YF₃: Eu³⁺ and YF₃: (Eu³⁺, Nd³⁺) Nanoparticles for Optical Temperature Sensing

Abstract

YF3: (Eu3+, Nd3+) nanoparticles (orthorhombic phase, D~130 nm) were synthesized via the co-precipitation method, with subsequent hydrothermal treatment and annealing. The Eu3+ τdecay linearly descends with the increase of temperature in the 80–320 K range. The τdecay (T) slope values of the annealed YF3: Eu3+ (2.5 and 5.0 mol.%) nanoparticles were the highest (110·10−4 and 67·10−4, μs/K) in the whole 80–320 K range, respectively. Thus, these samples were chosen for further doping with Nd3+. The maximum Sa and Sr values based on the LIR (IEu/INd) function were 0.067 K−1 (at 80 K) and 0.86%·K−1 (at 154 K), respectively. As mentioned above, the single-doped YF3: Eu3+ (2.5%) nanoparticles showed the linearly decreasing τdecay (T) function (5D0–7F1 emission). The main idea of Nd3+ co-doping was to increase this slope value (as well as the sensitivity) by increasing the rate of τdecay (T) descent via the addition of one more temperature-dependent channel of 5D0 excited state depopulation. Indeed, we managed to increase the slope (Sa) to 180·10−4 K−1 at 80 K. This result is one of the highest compared to the world analogs.

Keywords

• lifetime thermometry
• Nd³⁺/Yb³⁺
• Nd³⁺/Yb³⁺:YF₃
• down-conversion
• optical temperature sensors