Transmissive fluorescent temperature sensor based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber for real-time thermal monitoring of motors using the FIR technique

In this paper, we fabricate a transmissive fluorescent temperature sensor (TFTS) that based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber, which has the advantages of compactness and simplicity, corrosion resistance, high stability and anti-electromagnetic interference. The doping of Mo6+ ions will enhance the up-conversion (UC) fluorescence emission efficiency of Er3+ ions, thus improving the signal-to-noise ratio of TFTS. Using the fluorescence intensity ratio (FIR) technique, the real-time thermal monitoring performance of TFTS is evaluated experimentally. Apart from good stability, its maximum relative sensitivity is 0.01068 K-1 at 274 K in the measured temperature range. In addition, it is successfully used to monitor the temperature variation of the stator core and stator winding of the motor in actual operation. The results show that the maximum error between the FIR-demodulated temperature and the reference temperature is less than 1.2 K, which fully confirms the effectiveness of the TFTS for temperature monitoring. Finally, the FIR-based TFTS in this work is expected to provide a new solution for accurate and real-time thermal monitoring of motors and the like.

Spectral Investigation of Yb3+/Ho3+/Tm3+:Y2Si2O7 Upconverting Nanophosphors for the Usage of Temperature Sensing

Rare earth (Yb3+, Ho3+, Tm3+) yttrium disilicate phosphors were produced by sol-gel technique and heated at 1050 °C temperature. The sizes of the phosphors vary between 20-30 nm according to the images obtained from the Transmission Electron Microscope. The up-conversion (UC) emissions of the nanopowders were measured in the range of 500–900 nm wavelength under 950 nm laser excitation. A linear increase with power was observed in the emission intensity ratio depending on the laser excitation power. Using the FIR technique, the phosphor’s temperature was determined by the heating effect caused by the laser pump power. Due to the change in intensity ratio versus temperature, the temperature sensitivity at 428 K was calculated as 0.781x10-2K-1 and it was suggested that it can be used as a promising temperature sensor probe in photonic devices.

Upconversion Yb3+/Er3+:La2Ti2O7 phosphors for solid-state lighting and optical thermometry

The solid-state reaction was employed as a suitable method to produce orthorhombic Yb³⁺/Er³⁺ co-doped La₂Ti₂O₇ phosphors. The pump power and temperature dependencies of spectra of the Yb³⁺/Er³⁺ co-doped La₂Ti₂O₇ were studied for color tunability and optical thermometry. The pump power significantly affected the color coordinates of the phosphors. The upconversion green light transformed to the broad white light at higher pump power. A two-photon transition was proposed to explain the upconversion energy transfer process. The fluorescence intensity ratio technique was used to calculate the optical temperature sensor sensitivities. The ΔE energy difference obtained from the intensity ratios of the thermally coupled ²H_11/2 and ⁴I_15/2 energy levels of Er³⁺ are 763.64 ± 76.62 cm^-1, 777.77 ± 44.62 cm^-1, 640.71 ± 137.39 cm^-1 for La_1.95Yb_0.04Er_0.01Ti₂O₇, La_1.94Yb_0.04Er_0.02Ti₂O₇, and La_1.93Yb_0.04Er_0.03Ti₂O₇, respectively. Absolute temperature sensitivities of the phosphors decreased with increasing Er³⁺ concentration. The maximum absolute sensitivity was determined to be 0.51x10^-2 K^-1 at 553 K for La_1.95Yb_0.04Er_0.01Ti₂O₇, 0.64x10^-2 K^-1 at 571 K for La_1.94Yb_0.04Er_0.02Ti₂O₇, and 0.38x10^-2 K^-1 at 457 K for La_1.93Yb_0.04Er_0.03Ti₂O₇.