Enhancing the temperature measurement range of the Mn4+ ion sideband through cation substitution and adjustment of the excitation wavelength

Researchers have extensively contemplated the meticulous design and development of optical thermometers utilizing luminescent materials, owing to their distinct advantages, including rapid measurement speed, exceptional sensitivity, and the absence of intrusion-related damage. However, the exploration of optical thermometers with ultra-wide temperature measurement ranges still poses a significant challenge. In this study, we employed a cation substitution strategy to optimize the luminescence performance of Mn⁴⁺-doped phosphors. Specifically, the substitution of cations after Sn⁴⁺ doping resulted in an elevation of the energy level of Mn^{4+ 4}T_2g, which effectively inhibited non-radiative transitions. Consequently, it increased the quenching temperature in the Mg₂₈Ge_6.4Sn_1.1O₃₂F_15.04:0.05Mn⁴⁺ phosphor. Subsequently, we conducted a systematic investigation into the impact of excitation wavelengths on the quenching temperature of the material. Utilizing its high quenching temperature and the differential responses of Stokes and anti-Stokes lines to temperature, we performed a thermometry study across a broad temperature range spanning from 100 K at low temperatures to 800 K at high temperatures. At three representative excitation wavelengths with excellent thermal stability (418 nm, 365 nm, and 456 nm), we observed high relative sensitivities of 3.43 % K⁻¹, 3.71 % K⁻¹, and 4.57 % K⁻¹, respectively. This work demonstrates the promising potential of designing Boltzmann ratio optical thermometers using transition metal Mn⁴⁺ ions.