In this work, the potential of Li1.8Na0.2TiO3: Mn4+ for the lifetime-based luminescence thermometry is assessed. The material is prepared by the solid-state reaction of Li2CO3, Na2CO3, and nanostructured TiO2 at 800°C, and its monoclinic structure (space group C2/c) is confirmed by X-ray diffraction analysis. In this host, Mn4+ provides strong absorption around 330 nm and 500 nm due to 4A2g → 4T1g and 4A2g → 4T2g electric dipole forbidden and spin-allowed electron transitions, respectively, and emits around 679 nm on account of 2Eg → 4A2g spin forbidden electron transition. Temperature dependences of emission intensity and emission decay are measured over the 10–350 K range. Due to the low value of the energy of 4T2g level (20000 cm-1), the strong emission quenching starts at low-temperatures which favors the use of this material for the luminescence thermometry. It is demonstrated that the quite large value of relative sensitivity (2.6% K-1@340 K) facilitates temperature measurements with temperature resolution better than 0.1 K, and with the excellent repeatability.

This project has received funding from the European Union's Horizon 2020 FET Open programme under grant agreement No 801305 (NanoTBtech).