Enhanced red up-conversion emission in Er3+/Yb3+ co-doped SrSnO3 for optical temperature sensing based on thermally and non-thermally coupled levels

In this work, the synthesis and characterization of SrSnO3:Er3+ 1% co-doped with Yb3+ x% (x = 1, 3, 5 and 7%) are shown. The synthesis was carried out by a modified sol-gel method. All the samples were characterized by X-ray powder diffraction and luminescence spectroscopy. All the synthesized phases have been indexed as distorted orthorhombic structures of SrSnO3 with the space group Pbnm. This study focuses on the optical properties of the doped and co-doped matrix. The up-conversion emission and optical temperature sensing properties of thermally and non-thermally coupled levels show the importance of co-doping with Yb3+ ions. The intensity of both green emissions, at 523 and 550 nm, increases when the co-doping of Yb3+ increases up to 5%, and then decreases. In the same way, the red emission (660 nm) increases in a more significant way when Yb3+ ions are present compared to when they are not in the matrix, showing the importance of Yb3+ as a co-dopant. The temperature sensing properties indicate the dependence of luminescence on temperature. To study this relationship, the fluorescence intensity ratio technique was used. The spectra were measured exciting at 975 nm while the sample was heated in a temperature range between 285 and 405 K, showing that the temperature dependence obtained for the intensity ratio (660/550) of these non-thermally coupled levels is temperature dependent and can be compared and studied as a temperature sensor. To study the performance and applicability of the material, the detection sensitivity, relative sensitivity and uncertainty temperature values were obtained. The excellent value obtained for the uncertainty temperature (approximately 0.1 K) using TCL indicates that the present material may be used as an effective temperature sensing device.