Er³⁺ doped ferroelectric Pb(Mg_1/3Nb_2/3)O₃–0.25PbTiO₃ ceramic used as a linear response fluorescent temperature sensor

Er³⁺ doped ferroelectric Pb(Mg_1/3Nb_2/3)O₃–0.25PbTiO₃ (PMN–PT) ceramic was grown by using a two-stage sintering method. The sample shows relatively strong upconversion (UC) visible fluorescence under a 980 nm diode laser excitation and the fluorescence spectra were recorded in the temperature (T) range of 300–600 K. The fluorescence intensity ratios (FIR) of different energy levels, like ²H_11/2, ⁴S_3/2, ⁴F_9/2, and its stark sublevels, were studied as functions of temperature. The responses of FIR adopted here have a linear response to temperature in certain temperature range, and the resolutions achieved for temperature sensing using this material can be 0.5 K with the sensitivity as high as 2.9% K⁻¹.