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The description of luminescent processes and their thermally induced changes, that may be also influenced by the optically active ions concentration, and thus by the various inter-ionic processes, is the key to the improved development of luminescence thermometry. A phosphor doped with only trivalent terbium ions was described, which, by using two excitation lines fitted to the 7F6 → 5D3 and 7F5 → 5D3 transitions, shows a luminescent signals with the opposite characteristics of intensity changes as a function of temperature. By modifying the concentration of Tb3+ ions, the probability of {5D3, 7F6} ↔ {5D4, 7F0} cross-relaxation was being altered, which turned out to have a beneficial effect on the properties of the described nanothermometers. The ratio of intensities for both excitations was found to be temperature dependent, which resulted in high relative sensitivities of temperature readout reaching 3.2%/°C for 190 °C and not reaching values below 2%/°C in the broad range of the temperature. Extensive decay time measurements for 5D3 and 5D4 emissive levels were presented and the variability of both rise- and decay times as a function of terbium concentration and temperature was investigated. Thanks to this, conclusions were drawn regarding thermally dependent optical processes occurring in a given and similar systems.

Responding to the latest trends in luminescence thermometry, a new material of TZPN glass doped with Tb3+ ions was investigated for its use in the single band ratiometric approach. In contrast to the most of the Tb3+ doped phosphors emission intensity of Tb3+ ions in TZPN glass upon excitation matched to transitions from the ground 7F6 level show strong thermal quenching of luminescence intensity. On the other hand for an excitation line matched to the absorption from the thermally coupled excited 7F5 level, the emission intensity increases for temperature elevation. The ratio of these two signals is known to be an excellent temperature dependent parameter enabling a highly sensitive temperature readout. Strong thermal quenching of Tb3+ emission was discussed in terms of the thermally induced electron transfer from f state to the conduction band of the glass. In this work, it has been shown that optimization of the thermal quenching process is as important as the previously proposed optimizations of the intensity variability upon stimulation matched to excited state absorption. High relative sensitivities reaching 1–2%/°C were achieved, mainly because of the strong thermal quenching of the luminescence exhibited by the TZPN: Tb3+ glasses with different concentrations of dopant ions.