Optical thermometry based on upconversion emission of Yb3+/Er3+ codoped bismuth titanate microcrystals

Optical thermometry has drawn great attention due to its sensitive and noncontact properties. Herein, Yb3+/Er3+ codoped Bi4Ti3O12 phosphor microcrystals have been synthesized by solid phase reaction for optical temperature sensing. The phase, microscopic structure and morphology of the prepared sample have been studied by the Xray diffraction, transmission electron microscopy, etc. The process of upconversion emission has been researched with different environmental temperature and excitation power under 980 nm laser excitation. Meanwhile, the temperature sensing nature of the as-prepared microcrystals has been investigated based on the luminescence intensity ratio of two thermally coupled energy levels (Er3+:H-2(11/2), S-4(3/2)). The excitation laser power density is 3.95 mW/mm(2), and the absolute sensitivity reaches 0.0046 K-1. The result demonstrates potential of the Bi4Ti3O12:Yb3+/Er3+ microcrystals in making optical sensing device under low excitation power density.