The excellent dual optical thermometry of the Yb³⁺, Er³⁺ doped SrLu₂O₄

SrLu₂O₄: Yb³⁺, Er³⁺ samples were achieved successfully via a traditional solid-state method at 1450 °C. As 980-nm laser exciting, the UC spectra include red and green emissions mainly centering on 665 and 552 nm, respectively. The red is dominant, and the green part is a relative weakness. For all co-doped samples, intense red radiation is obtained. Meanwhile, the experimental formulas about pumping power and spectrum intensity helped us comprehend the up-conversion processes further, and the conclusion is a two-photon process in UC. The ⁴S_3/2 and ²H_11/2 levels ions are thermal coupled energy levels. We also investigated thermometric characteristics of the samples on the fluorescence intensity ration technology. For SrLu₂O₄: Er³⁺/Yb³⁺, it can be used as a temperature sensor by using its green emission and red emission, and the sensor sensitivity was calculated. The maximum absolute sensitivity and the relative sensitivity is 0.00226 K^-1 and 0.0119 K⁻¹ at 513 K for green emission and the maximum absolute sensitivity and the relative sensitivity is 0.00126 K^-1 and 0.0026 K⁻¹ at 303 K for red emission. The fluorescence intensity ratio (FIR) values are almost stable and accurate in repeated tests. As a result, the SrLu₂O₄: Er³⁺/Yb³⁺ samples would useful hopefully to optical engineering and sensors.