Synthesis and Er3+ spectroscopic property of Er3+/Yb3+-codoped CaIn2O4 nano-fibers for thermometry

Er 3+ /Yb 3+ -codoped CaIn 2 O 4 nano-fibers with good morphology were synthesized by electrospinning technique. X-ray diffraction was performed on the synthesized phosphor of nano-fibers to confirm that the CaIn 2 O 4 crystalline phase is dominant in it. The morphology of the nano-fibers was characterized by scanning electron microscopy. Optimal power supply voltage and thickener concentration for the synthesis were obtained. Er 3+ 980-nm-upconverted emission characteristics of the nano-fibers were investigated. The results show that two-photon process is the dominant mechanism for the upconversion emissions. The nano-fibers doped with 5 mol% Er 3+ display the strongest upconversion fluorescence. Temperature characteristics of the green 530 and 550 nm upconversion fluorescence of the nano-fibers were also studied for thermometry purposes. The results reveal that the nano-fibers show thermally stable spectral structure and the ones doped with 5 mol% Er 3+ display the highest thermal sensitivity of green fluorescence intensity ratio. We conclude that there exists an optimal Er 3+ concentration of 5 mol%, and the CaIn 2 O 4 nano-fibers doped with this optimal Er 3+ concentration display some spectroscopic properties favorable for ratiometric thermometry in the high-temperature regime.