Two ratiometric thermometry methods based on the interplay between Eu 2 + and Eu 3 + and single Eu 3 + emissions on OH − -free low-silica calcium aluminosilicate glass

The constant demand to accurately measure the temperature sheds light on luminescent materials that have dependence on their thermodynamic quantities. Several materials have been applied as sensors to measure temperature for different applications, however, very few showed high precision and sensitivity. This work reports the Eu${}^{2+}$/Eu${}^{3+}$-doped low-silica calcium aluminosilicate glass as a potential candidate for high sensitive ratiometric thermometer. The glass was analyzed close to the physiological temperature range, between 288.15 – 333.15 K. Since this glassy matrix provides the presence of two europium valences, two different approaches are presented. The first takes into account the temperature dependence of ${}^5$D${}_0$ $\to$ ${}^7$F${}_4$ emission for two different excitation wavelengths, and the second one is based on the interplay between Eu${}^{2+}$ and Eu${}^{3+}$ emissions. Both ratiometric approaches presented high reproducibility and relative sensitivity values, from 1.2 to 1.6 %/K and from 0.75 to 0.95 %/K, for the first and second approach, respectively.