Codoping Pr and Er into NaLaTiO to realize dual-mode FIR temperature sensing properties.

In this report, a Pr/Er doped NaLaTiO 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 Pr singly doped NaLaTiO material. In addition, the material showed typical 4f-4f transitions with two dominant bands around 495 nm and 609 nm originating from P → H and D → H, respectively, upon ICVT or Pr unique 4f-4f excitation. In Pr, Er co-doped samples, the up-conversion (UC) emission bands around 522 nm, 548 nm and 661 nm, originating from characteristic transitions H → I, S → I and F → I of Er ion was found, respectively, upon 980 nm radiation. Besides, the four main bands around 495 nm, 522 nm, 543 nm, 609 nm assigned to PrP → H, ErH → I, ErS → I, PrD → H, 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 NaLaTiO:Pr, Er. Additionally, the maximal absolute temperature sensitivity S and relative temperature sensitivity S reach 0.0831 K at 294 K and 1.15 % K at 294 K under 980 nm excitation mode, and 0.01742 K at 453 K and 1.826 % K 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 Pr and Er into suitable matrices to devise excellent FIR optical thermometry.