Optical thermometry through infrared excited green upconversion in monoclinic phase Gd₂(MoO₄)₃:Yb³⁺/Er³⁺ phosphor

Monoclinic phase Gd₂(MoO₄)₃: Yb³⁺/Er³⁺ phosphor is synthesized via a simple sol-gel method. The XRD result reveals that the phosphor possesses monoclinic structure with space group C2/c(15). Under the excitation of a 980 nm laser, its emission spectra shows remarkably intense green and negligible red emissions, which are all two-photon process. By investigating effect of temperature on green emission of the sample, the competition between the thermal agitation and non-radiative relaxation of ²H_11/2 level can be found, which is verified by the measurement of lifetime. In addition, the sensitivity of optical thermometry is studied based on the fluorescence intensity ratio technique through infrared excited green upconversion. The maximum sensitivity is found to be about 0.02574 K⁻¹ at 510.2 K, suggesting that the phosphor can be used as an excellent material for optical temperature sensing.