Explaining the temperature-induced shift of the V-O charge transfer band experimentally and design of single-excitation ratiometric optical thermometry

Temperature-induced redshift of the V-O charge transfer band (CTB) is promising for designing high performance optical thermometry. The shift mechanism is considered as the thermal populations of high vibrational energy levels of the VO 4 3− ground state. Direct experimental evidence for this, however, is still lacking. In this work, Tm 3+ -doped YVO 4 with various doping concentrations was studied to achieve strong 1 D 2 emission of Tm 3+ . The temperature dependent CTB was studied at low temperatures to give direct evidence experimentally for the shift mechanism of the CTB using YVO 4 :20% Tm 3+ . It was found that the V-O CTB does not shift when the temperature is lower than a certain temperature (60 K), verifying the proposed shift mechanism experimentally. In addition, based on the temperature quenching of 1 D 2 emission of Tm 3+ and the redshift of the CTB, single-excitation ratiometric thermometry was carried out using YVO 4 :30% Tm 3+ ,6% Sm 3+ . High relative sensitivity was achieved with a maximal value reaching up to 3.86% K −1 at approximately 355 K.