Defect elimination to enhance photoluminescence and optical transparency of Pr-doped ceramics for self-calibrated temperature feedback windows
Kailei Lu, Yucheng Ye, Wenhan Han, Gang Cheng, Xinghua Zhu, Jianqi Qi, Tien‐Chang Lu
Abstract
Pr-doped metal oxide polycrystalline transparent ceramics are highly desirable for photothermal window systems served in extreme environments; however, obtaining efficient photoluminescence (PL) together with high transparency in these ceramics is still posing serious challenges, which undoubtedly limits their applications. Here, Pr-doped Y<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (YZO) transparent ceramics, as an illustrative example, are prepared by a solid-state reaction and vacuum sintering method. Owing to the elimination of defect clusters [<inline-formula> <math display="inline" id="MA1"><mrow><msubsup><mrow><mtext>Pr</mtext></mrow><mtext>Y</mtext><mrow><mn>4</mn><mo>+</mo></mrow></msubsup><mo>−</mo><msup><mtext>O</mtext><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>−</mo><msubsup><mrow><mtext>Pr</mtext></mrow><mtext>Y</mtext><mrow><mn>4</mn><mo>+</mo></mrow></msubsup></mrow></math></inline-formula>] and [<inline-formula> <math display="inline" id="MA2"><mrow><msubsup><mrow><mtext>Pr</mtext></mrow><mtext>Y</mtext><mrow><mn>4</mn><mo>+</mo></mrow></msubsup><mo>−</mo><msup><mtext>e</mtext><mo>′</mo></msup></mrow></math></inline-formula>] without the introduction of impurities and additional defects, the fabricated YZO:Pr ceramics exhibit high transparency (74%) and efficient PL (39-fold enhanced) after air annealing plus vacuum re-annealing treatment. Moreover, upon 295/450 nm excitation, the emission bands (blue, green, red, and dark red) from YZO:Pr ceramics present different temperature-dependent properties due to the thermal-quenching channel generated by the intervalence charge transfer (IVCT) state between Pr<sup>3+</sup> and Zr<sup>4+</sup> ions. Furthermore, a self-calibrated temperature feedback window with the same fluorescence intensity ratio (FIR) model (<i>I</i><sub>613</sub>/<i>I</i><sub>503</sub>, where <i>I</i> represents the intensity) under different excitation light sources (295 and 450 nm) is designed. The developed photothermal window operated in a wide temperature range (303–663 K) shows relatively high sensitivities (absolute sensitivity (<i>S</i><sub>a</sub>) and relative sensitivity (<i>S</i><sub>r</sub>) reach 0.008 K<sup>−1</sup> at 663 K and 0.47% K<sup>−1</sup> at 363 K, respectively), high repeatability (> 98%), and low temperature uncertainty (<i>δT</i> < 3.2 K). This work presents a paradigm for achieving enhanced PL along with elevated transparency of lanthanide (Ln)-doped ceramics through vacuum re-annealing treatment engineering and demonstrates their promising potential for photothermal window systems.