Lanthanide Ion-Doped Bismuth Titanate Nanocomposites for Ratiometric Thermometry with Low Pump Power Density

The sensing of temperature is closely related to human life. The noncontact ratio temperature measurement method has extensive applications in biochemical monitoring and industrial production. However, optical detection techniques based on fluorescence intensity ratio (FIR) still face many challenges, such as laser thermal effects, accuracy, and reversibility. In this article, the Yb3+/Er3+-codoped Bi4Ti3O12 nanocrystalline composite has been developed for thermometer. The introduction of Bi4Ti3O12 nanocrystals into the glass matrix exceptionally enhances the upconversion emission of Er3+ ions. The Yb3+/Er3+-codoped Bi4Ti3O12 nanocrystalline composite enables online temperature measurement under low power excitation density (0.75 W/cm2), which can reduce the thermal effect of the laser. In addition, Yb3+/Er3+-codoped nanocrystalline composite has excellent precision of temperature measurement in the temperature range of 293–573 K. The value of absolute sensitivity S a is 5.2 × 10–3. The maximum value of the relative error between the measured temperature and the actual temperature does not exceed 0.4% in the reliability test, and temperature measurement has excellent repeatability. Therefore, the developed Yb3+/Er3+-codoped nanocrystalline composite is a promising candidate for ratiometric thermometry.