Up-conversion luminescence lifetime thermometry based on the ¹G₄ state of Tm³⁺ modulated by cross relaxation...

β-PbF₂:Tm³⁺/Yb³⁺ glass ceramics (GCs) with varied Tm³⁺ doped concentrations were synthesized by the conventional melting-quenching method and the subsequent glass crystallization route. For the first time, the lifetime-based thermometer based on up-conversion luminescence (UCL) originating from the ¹G₄ state excited upon a miniaturized 976 nm diode laser excitation in β-PbF₂:Tm³⁺/Yb³⁺ GCs is achieved. Furthermore, the thermosensitivity of the ¹G₄ state lifetime is realized by the phonon-assisted cross relaxation (CR) processes between Tm³⁺ which depopulate the ¹G₄ state and get severer with temperature. The relative sensitivity (S_R) of the ¹G₄ state lifetime is promoted by intensifying CR processes via raising Tm³⁺ concentration in this work. The maximum values of S_R of ¹G₄ state lifetime obtained in 0.0005Tm, 0.01Tm and 0.05Tm are 0.16%K^-1, 0.26%K^-1, and 0.46%K^-1 at 488 K, respectively, which indicates the potential ability of Tm³⁺-doped nanoparticles to work as indicators for UCL lifetime-based thermometers.