Origin of the temperature-induced redshift of the charge transfer band of GdVO_4

Abstract

The charge transfer band (CTB) of the VO43− groups in vanadates shifts to longer wavelengths with increasing temperature. The origin of this temperature-induced redshift was explored by studying the temperature-dependent excitation and emission spectra of GdVO4 ranging from 300 to 480 K. The influences of the thermal population and the decline of the charge transfer gap on the spectral shift were analyzed using the configurational coordinate diagram. We conclude that the thermal population of vibrational sublevels of the ground electronic energy level dominates the temperature-induced redshift of the CTB. Taking advantage of the redshift and the thermal quenching, a novel ratiometric temperature-sensing strategy was proposed. Drastic temperature dependence was achieved, indicating a promising candidate for an optical thermometer with high sensing performance.