To shift the onset of thermal quenching by multiphonon emission to higher temperatures, thermographic phosphors for high-temperature applications are usually selected with a large energy gap between the radiatively emitting energy level and the next lowest energy level. An alternate approach is presented where Y2O3:Er, with a relatively small energy gap of 2795 cm−1 between the 4S3/2 emitting level and the 4F9/2 level below it, provides effective temperature measurements from room temperature to 1200 °C. The smaller energy gap results in an expanded temperature measurement range because (1) it results in a lower temperature onset of thermal quenching by multiphonon emission and (2) the smaller number of phonons required to bridge the energy gap produces a weaker temperature-dependent increase in multiphonon emission rates with temperature. Utilizing the intense hypersensitive 4I15/2 → 2H11/2 Er3+excitation at 522 nm offsets the temperature precision reduction due to the decreased decay time temperature sensitivity. Two distinct temperature sensitivity ranges are observed due to a crossover in multiphonon emission relaxation from high to low effective phonon energies at about 950 °C. The implications of this transition from high to low effective phonon energies for selection of dopant hosts for high-temperature thermographic phosphor applications are discussed.