Luminescence kinetic characterization of CeF3-YF3-TbF3 nanoparticles for lifetime temperature sensing

The Ce_0.5Y_0.5-XTb_XF₃ (X = 0.001, 0.01, 0.05, 0.1, and 0.2) nanoparticles were synthesized via the co-precipitation method. The samples demonstrated average diameters around 20 nm and hexagonal phase corresponding to the CeF₃ matrix. Under 266 nm excitation (4f – 5d absorption band of Ce³⁺), all the samples showed bright green luminescence of Tb³⁺. In turn, the effective decay times (τ_eff) demonstrated the complicated temperature dependence in the 303–523 temperature range including rising and decaying parts. We suggested two hypotheses explaining such temperature dependence of τ_eff of Tb³⁺. The first one is related to the thermal expansion phenomenon when Tb³⁺ ions distance from each other with the temperature increase and the efficiency of the concentration quenching decreases. The second hypothesis suggests that the excitation of Tb³⁺ is performed through both Ce³⁺ ions or crystal lattice defects. In the case of defects, they “collect” the excitation energy and then populate Tb³⁺ ions. The efficiency of this population increases with the increase of temperature which leads to the increase of the lifetime of Tb³⁺. The decreasing part of the τ_eff function at higher temperatures was explained by the contribution of multi-phonon quenching of the luminescence. The studied Ce_0.5Y_0.5-XTb_XF₃ (X = 0.001, 0.01, 0.05, 0.1, and 0.2) samples showed competitive performances. Specifically, the maximal S_r values are in the 0.2–0.4 %/K range.