Up-conversion luminescence of LiTaO3:Er3+ phosphors for optical thermometry

Abstract We synthesized LiTaO3:Er3+ phosphors by molten salt method, and systematically investigated their phase structure, micro-morphology, up-conversion luminescence, and optical temperature sensing properties. The up-conversion luminescence was demonstrated to arise from two near-infrared photon absorption process, which can be optimized by tuning Er3+ dopant concentration. The corresponding mechanism was proposed based on the transitions between dopant states as illustrated in an energy level diagram. The optical temperature sensing properties were explored by utilizing the fluorescence intensity ratio method. Notably, a wide operation scope ranging from 100 to 500 K was obtained, along with a relatively large energy gap (ΔE = 698 cm−1) and a high absolute sensitivity (Sa = 3.34 × 10−3 K−1 at 492 K). The impressive properties of LiTaO3:Er3+ phosphors in combination with the incomparable multifunctional feature of host material reveal their potential for developing integratable up-conversion optical thermometry.