Optical temperature sensor based on upconversion luminescence of Er3+ doped GdTaO4 phosphors

Abstract

AbstractFor the development of optical temperature sensor, a series of GdTaO4 phosphors with various Er3+‐doping concentrations (0, 1, 5, 10, 25, 35, 50 mol%) were synthesized by a solid‐state reaction method. The monoclinic crystalline structure of the prepared samples was determined by X‐ray diffraction (XRD). Under excitations of 980 and 1550 nm lasers, the multi‐photon‐excited green and red upconversion (UC) luminescence emissions of Er3+ were studied, and the critical quenching concentration of Er3+‐doped GdTaO4 phosphor was derived to be 25 mol%. By changing the pump power of laser, it was found that the two‐photon and three‐photon population processes happened for the UC emissions of Er3+‐doped GdTaO4 phosphors excited by 980 and 1550 nm lasers, respectively. Furthermore, based on the change of thermo‐responsive green UC luminescence intensity corresponding to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ with temperature, the optical temperature sensing properties of Er3+‐doped GdTaO4 phosphor were investigated under excitations of 980 and 1550 nm lasers by using the fluorescence intensity ratio (FIR) technique. It was obtained that the maximum absolute sensitivity (SA) and relative sensitivity (SR) of Er3+‐doped GdTaO4 phosphors are as high as 0.0041 K−1 at 475 K and 0.0112 K−1 at 293 K, respectively. These significant results suggest that the Er3+‐doped GdTaO4 phosphors are a promising candidate for optical temperature sensor.