A dual-mode self-referenced optical thermometry with high sensitivity based on Er3+-Yb3+ co-doped Sr2YTaO6 thermochromic phosphor

Up conversion luminescent materials Sr2YTaO6: Er3+, Yb3+ phosphors were prepared by high temperature calcination. In view of the formation, temperature characteristics, and photoluminescence features of the sample, X-ray diffraction and photoluminescence were used. Under the excitation at 980 nm, the series of samples is significantly stimulated by Er3+ up-conversion luminescence and Yb3+ sensitization at 524, 550 and 659 nm. According to the diversity of temperature sensing performance from these three highest peaks, a dual-mode temperature sensor on account of fluorescence intensity ratio (thermally coupled level between 2H11/2 and 4S3/2, and nonthermally coupled energy levels between 2H11/2 and 4F9/2) is achieved by using a single luminescent center. Moreover, the phosphor has strong thermal stability, which is helpful to improve the accuracy of temperature measurement. Under the temperature measurement of a dual-mode temperature sensor, it is calculated that the optimal absolute sensitivity Sa of thermally coupled energy level is 0.78 × 10−3 K−1 (473 K) and relative sensitivity Sr is 1.32 %K−1 (293 K), and the maximum optimal absolute sensitivity Sa of non-thermally coupled energy level is 1.02 × 10−4 K−1 (473 K) and relative sensitivity Sr is 0.58 %K−1 (293 K). All results imply that Sr2YTaO6: Er3+, Yb3+ phosphors are promising materials for self-referenced optical temperature measurement.