An optical thermometry based on abnormal negative thermal quenching of the charge transfer band edge

In this work the temperature-dependent photoluminescence excitation and photoluminescence spectroscopies of Eu3+ tdoped LuVO4 phosphors have been performed in the 298-448 K range. It is found that the charge transfer band (CTB) of [VO4](3-) unites undergoes a red-shift, mainly owing to thermal population of the vibronic sublevels of the ground electronic energy level, as the temperature increases. Due to this, the edge of CTB in PLE exhibits an abnormal negative thermal quenching behavior compared to those of the maximum CTB transition and the intra-configuration f-f transitions of Eu3+ ions. Accordingly, a novel thermometry strategy for realizing ratiometric optical thermometer is proposed by considering different excitation paths taking advantage of their diverse thermal behaviors. For Eu3+-doped LuVO4 compound, our experimental results demonstrate its great potential for high performance optical thermometry, promising with a remarkable relative sensitivity and excellent repeatability in the 298-448 K range.