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Title: NIR-to-NIR lifetime based thermometry with the thermally elongated luminescence kinetics driven by structural phase transition in LiYO2:Yb3+

Authors: M. T. Abbas, M. Szymczak, V. Kinzhybalo, M. Drozd, L. Marciniak

Journal: Laser & Photonics Reviews

DOI: 10.1002/lpor.202401108  

Continuing their research on luminescence thermometers based on thermally induced structural phase transitions in inorganic materials doped with lanthanide ions, Prof. Marciniak's group has demonstrated that the increase in symmetry in LiYO₂ significantly modifies the spectroscopic properties of Yb³⁺ ions. These changes are evidenced not only by alterations in the energies of the Stark levels of Yb³⁺ ions, leading to modifications in the shape of emission spectrum, but also by variations in luminescence kinetics. Specifically, an increase in the symmetry of the crystallographic site occupied by Yb³⁺ ions from C₂ to D_2d modifies the probability of radiative depopulation of the ²F_5/2 level. Consequently, a thermally induced elongation of the luminescence decay corresponding to the ²F_5/2 → ²F_7/2 electronic transition is observed. This unique effect can be utilized in remote temperature sensing. The sensitivity of such a thermometer is 0.5% K^-1 near the phase transition temperature, which can be controlled by adjusting the dopant ion concentration. Additionally, the sensitivity of a ratiometric luminescence thermometer based on the Stark lines of the ²F_5/2 → ²F_7/2 band is 5.3% K^-1 at 280 K for LiYO₂:5%Yb³⁺.

The work presented was funded under the NCN Opus project UMO-2022/45/B/ST5/01629.