Role of Er3+ concentration on the photoluminescence and temperature sensing properties in Er3+ doped Y2O3 based transparent ceramics

The photoluminescence and temperature sensing properties of Er3+ doped Y2O3 based transparent ceramics have been studied as a function of Er3+ doping concentration. The samples exhibit high transparency thanks to the homogeneous microstructure with no obvious impurities or pores. Under 980 nm excitation, strong visible upconversion (UC) and near infrared (NIR) emissions of Er3+ ions are observed. By using the fluorescent intensity ratio (FIR) technique, the temperature sensing properties are investigated based on the thermally coupled levels H-2(11/2) and S-4(3/2) (FIR-1 = I-544/I-569) and non-thermally coupled levels F-4(9/2) and S-4(3/2) (FIR-2 = I-666/I-569) of Er3+ ions, respectively. The Judd-Ofelt (J-O) theory analysis reveals that the local crystal field around Er3+ ion changes with the doping concentration, leading to the tuned absolute sensing sensitivity (S-a) based on FIR-1. As for FIR-2, the sensing sensitivities of the samples enhance with the increasing Er a + content due to the promoted nonradiative processes (including S-4(3/2) -> F-4(9/2) and F-4(7/2) + I-4(11/2) -> E-4(9/2) + F-4(9/2)). The optimal S-a reaches similar to 371.8 x 10(-4)K(-1) in 6 mol% Er3+ doped sample, ranking among the highest ones for the luminescent materials.