Optical temperature sensing based on the near-infrared emissions from Nd³⁺/Yb³⁺ codoped CaWO₄

Under a 980 nm diode laser excitation, the near-infrared (NIR) emissions from Nd³⁺:⁴F_7/2, ⁴F_5/2, and ⁴F_3/2 states in Nd³⁺/Yb³⁺ codoped CaWO4 powder were studied at temperatures ranging from 303 to 873 K. As the temperature increased, the NIR luminescence intensity was significantly enhanced and nearly 190-fold enhancement was achieved at 873 K compared with that at 303 K. By using the fluorescence intensity ratio technique, the thermometry behaviors through the NIR emissions were investigated. The results illustrate that the sensitivity and the accuracy achieved here are much higher than temperature sensors based on other rare earth ion doped materials.