Low temperature sensing behavior of upconversion luminescence in Er3+/Yb3+ codoped PLZT transparent ceramic

In this paper, low temperature sensing characteristic of upconversion luminescence in Er3+/Yb3+ codoped lead-lanthanum zirconate-titanate ferroelectric ceramics (PLZT) was investigated by fluorescence intensity ratios (FIRs). The upconversion emissions at 539 nm, 564 nm and 666 nm were observed from 10 K to 320 K by exciting at 980 nm. These emissions were assigned to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively. The temperature dependent emission intensities of upconversion luminescence were analyzed, from which the thermal excitation processes among the three levels system of 2H11/2, 4S3/2 and 4F9/2 were discovered. Based on this, the FIRs of 539 nm to 666 nm, 539 nm to 564 nm are studied, and the variation trends of them agree with the Boltzmann distribution of thermal coupled in the temperature range of 140-320 K. The temperature sensitivity of intensity ratio of 539 nm to 666 nm is 21.84×10−4 K−1 at 320 K, which is about 4 times than that of 539 nm to 564 nm. The temperature sensing performance can be improved by high valued ΔE of thermal coupled levels (TCLs). This paper shows that 2H11/2 and 4F9/2 of Er3+ are TCLs in PLZT, and the upconversion luminescence of Er3+/Yb3+ codoped PLZT transparent ceramic have a potential application in low temperature sensing above 140 K.