Non-contact fluorescence intensity ratio optical thermometer based on Yb3+/Nd3+ codoped Bi4Ti3O12 microcrystals

Optical thermometer based on the non-contact fluorescence intensity ratio technique of two thermally-couple levels has huge potential applications in many fields, such as the electric power industry and in-situ physiological measurements. In the paper, the Yb3+/Nd3+ codoped Bi4Ti3O12 nanocrystal ratio thermometer has prepared by solid-phase sintering. The two thermally-couple levels are Nd3+:4F7/2 (emission peak around 753 nm) and Nd3+:4F5/2 (emission peak at 805 nm), respectively. The optical thermometer has based on the upconversion in near-infrared luminescence under 980 nm excitation with low power of 1.87 W/cm2. Due to the relatively low pump power, the effect of the excitation heat effect on the material is reduced. This resulted in a relatively high relative sensitivity (SR = 1% K−1) in the temperature range of 323–573 K. In addition to the characteristics, the excellent repeatability (σ = 1.5%) of the fluorescence intensity ratio between the two Nd3+ emission peaks makes Yb3+/Nd3+ codoped Bi4Ti3O12 microcrystals a promising non-contact near-infrared ratio thermometer.