Optical temperature sensor based on the Nd3+ infrared thermalized emissions in a fluorotellurite glass

The temperature dependence of the infrared luminescence of a fluorotellurite glass doped with 0.01 and 2.5 mol% of Nd3+ ions was studied in order to use it as a high temperature sensing probe. For this purpose, the emission intensities of the (4S3/2, 4F7/2), (2H9/2, 4F5/2),4F3/2→4I9/2 transitions were measured in a wide range of temperatures from 300 upto 650 K. The changes in the emission profiles were calibrated by means of the fluorescence intensity ratio technique. The calibrations showed a strong dependence on the Nd3+ ions concentration, having the low-doped concentrated sample the best response to changes of temperature. The maximum value obtained for the thermal sensibility is 17×10−4 K−1 at 640 K, being one of the highest values found in the literature for Nd3+ optical temperature sensors. Finally, the experimental calibrations were compared with the theoretical temperature luminescence response calculated from the Judd-Ofelt theory.