Temperature sensor based on upconversion luminescence of Er3+-doped fluoroaluminate glasses

New Er3+-doped fluoroaluminate glasses were examined as a host matrix for optical temperature sensors. The upconversion spectra as a function of temperature have been measured in the temperature range from 20 degrees C (293 K) to 235 degrees C (508 K). The nature of the upconversion luminescence bands with maxima around 522 nm and 550 nm corresponding to the transitions from levels 2H(11/2),S-4(3/2) and F-4(9/2) to the ground state I-4(15) was explained basing on two -photon processes. The measured values of fluorescence intensity ratios (FIR) were approximated by a linear function with the slopes varying from 0.0022 to 0.0039. The sample doped with 0.1 mol. % of ErF3 has the steepest inclination and the best response to temperature changes. The maximum value of absolute thermal sensitivity Smax of 69 x 10(-4) degrees C-1 at 235 degrees C was obtained for the sample doped with 0.1 mol. % of ErF3. The S. value is one of the highest values for different glass hosts found in the literature. The data obtained show that new Er3+ doped fluoroaluminate glass of the composition under investigation is a good host matrix for sensing element in optical thermometry. (C) 2018 Elsevier B.V. All rights reserved.