Neodymium doped fluoroindogallate glasses as highly-sensitive luminescent non-contact thermometers

Trivalent neodymium (Nd3+) can be used as high performance temperature luminescent ion sensor, namely in the near infrared spectral region. The disadvantage presented in the use of this ion is that transitions from thermally coupled levels show very different emission intensities. In order to solve this critical problem we propose to use Nd3+-doped fluoroindogallate glasses with low phonon cutoff energy (500 cm−1) as the active medium. By using a dopant concentration that minimizes losses due to cross relaxation processes and detecting the emissions of the thermally coupled levels with a R928 photomultiplier, without correction response for the wavelength dependence of the intensity, we have succeeded in getting the highest relative thermal sensitivities so far observed, 2.5%⋅K−1 and 7.4%⋅K−1, for the 4F5/2 → 4I9/2/4F3/2 → 4I9/2 and 4F7/2 → 4I9/2/4F3/2 → 4I9/2 intensity ratios, respectively at 288 K.