Fluoroaluminate glasses with low phosphate content doped with Er3+/Yb3+ ions for up-conversion luminescence temperature sensors

Abstract

Fluoroaluminate glasses with low phosphate content doped with Er3+-Yb3+ ions were synthesized and their upconversion luminescence was investigated as a function of temperature. The Judd-Ofelt theory was used to predict the transition probabilities, branching and to calculate fluorescence intensity ratio and thermal sensitivity of the glasses for the excited states of Er3+ions in the glasses. The effect of Er3+and Yb3+ ions concentrations and phosphate content on the upconversion luminescence was studied in the range 300–700 K. The fluorescence intensity ratio of the thermally coupled 2H11/2 and 4S3/2 levels of Er3+ions was studied to determine the thermal sensitivity of the glasses. It was found that the maximum absolute sensitivity Smax of the glasses under study varies in the range of 27–43 × 10−4 K−1. The high values of Smax, high upconversion intensity and the ability of recording up-conversion spectra at low excitation powers make fluoroaluminate glasses with low phosphate content promising materials for optical temperature sensors.