Effect of Li+/Mg2+ co-doping and optical temperature sensing behavior in Y2Ti2O7: Er3+/Yb3+ upconverting phosphors

The Y 2 Ti 2 O 7 : Er 3+ /Yb 3+ phosphors co-doped with Li + and Li + /Mg 2+ ions were prepared via solid state reaction method. The effects of Li + and Mg 2+ co-doping on the structure and morphology of Y 2 Ti 2 O 7 : Er 3+ /Yb 3+ phosphors were investigated by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) spectra and field emission scanning electron microscopy (FESEM) observations. The 980 nm excitation assisted UC luminescence intensity for green and red band was enhanced by 8.7 and 14.3 times respectively after co-doping with Li + /Mg 2+ ions in Y 2 Ti 2 O 7 : Er 3+ /Yb 3+ , which could be explained based on the variations in crystal structure and particle size. Using the fluorescence intensity ratio (FIR) technique, the impact of 980 nm pump power on the thermometric behaviors was studied based on the thermally coupled levels of 2 H 11/2 and 4 S 3/2 of Er 3+ ions. Due to the unique thermal properties of the Y 2 Ti 2 O 7 host, the temperature increment caused by laser thermal effect was minimized, benefiting the consistency of FIR data over a wide range of pump power density. Besides, a high relative sensor sensitivity of 1.17%K −1 was obtained for Y 2 Ti 2 O 7 : Er 3+ /Yb 3+ /Li + /Mg 2+ phosphors. These characteristics may make the studied system applicable for optical temperature sensor with high accuracy.