Codoping Pr3+ and Er3+ into NaLaTi2O6 to realize dual-mode FIR temperature sensing properties

Abstract

In this report, a Pr3+/Er3+ doped NaLaTi2O6 phosphor was prepared as self-reference optical thermometer via a typical solid-state sintering method. The phase component, crystal structure and luminescence properties were elaborated in detail. A broad IVCT band along with several narrow 4f–4f excitation bands were readily found when monitored at 608 nm in Pr3+ singly doped NaLaTi2O6 material. In addition, the material showed typical 4f–4f transitions with two dominant bands around 495 nm and 609 nm originating from 3P0 → 3H4 and 1D2 → 3H4, respectively, upon ICVT or Pr3+ unique 4f–4f excitation. In Pr3+, Er3+ co-doped samples, the up-conversion (UC) emission bands around 522 nm, 548 nm and 661 nm, originating from characteristic transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 of Er3+ ion was found, respectively, upon 980 nm radiation. Besides, the four main bands around 495 nm, 522 nm, 543 nm, 609 nm assigned to Pr3+ 3P0 → 3H4, Er3+ 2H11/2 → 4I15/2, Er3+ 4S3/2 → 4I15/2, Pr3+ 1D2 → 3H4, respectively, can be observed upon 379 nm co-excitation. By monitoring thermal responses emission intensities of versatile transitions under UC and down-shift (DS) excitation modes, good temperature sensitivity and signal discriminability based on FIR technique have been achieved in phosphor NaLaTi2O6:Pr3+, Er3+. Additionally, the maximal absolute temperature sensitivity Sa and relative temperature sensitivity Sr reach 0.0831 K−1 at 294 K and 1.15 % K−1 at 294 K under 980 nm excitation mode, and 0.01742 K−1 at 453 K and 1.826 % K−1 at 294 K under 379 nm excitation mode, respectively, indicating the prepared material in this work can be considered as a latent candidate for optical thermometry. More inspired, this work sets up a new pathway of codoping Pr3+ and Er3+ into suitable matrices to devise excellent FIR optical thermometry.