The rapid development of near‐infrared (NIR) spectroscopic techniques has greatly stimulated the discovery of novel broadband NIR‐emitting phosphors as advanced light sources. Herein, a novel double‐perovskite phosphor La2MgHfO6:Cr3+/Yb3+ that displays ultra‐broadband NIR emissions with a full‐width at half maximum (FWHM) of 333 nm is reported. The remarkable luminescence property stems from the multiple crystallographic sites, relatively weak crystal field, and efficient Cr3‐to‐Yb3+ energy transfer (ET). The site occupation of Cr3+ is elaborately verified by the Rietveld refinement and first‐principles calculation. By controlling the ET process, the internal/external quantum efficiency (IQE/EQE), bandwidth, and thermal stability of NIR emissions are substantially improved. The as‐prepared phosphors are further integrated into a miniaturized NIR light‐emitting diode (LED) package, demonstrating superior performance in rapid nondestructive detection of structural failure in thin electronic cables. The results described here provide a novel pointcut for designing broadband NIR‐emitting phosphors with desired optical properties toward applications in industrial inspection and medical diagnosis.
Non‐contact ratiometric luminescence thermometry continues to gain popularity over decades due to its fascinating features of high accuracy, fast response, and simplicity. In this regard, rational design of optical thermometers with ultrahigh relative sensitivity and low temperature resolution has become a cutting‐edge topic. Herein, a luminescence intensity ratio thermometric method depending on the emission line at 698 nm (peak 1) and the emission bands at 713 and 721 nm (peaks 2 and 3) of Li1.97Zn1.0292Ge3O8:0.08%Cr3+ is proposed. As temperature elevates from 50 to 300 K, the 698 nm emission line undergoes an 84‐fold increase while the 713 and 721 nm emission bands show the opposite decline trend. This fascinating feature enables high relative sensitivity of 13.09% K−1 and low temperature resolution of 0.032 K, which are superior to most of the reported optical thermometers. This work is expected to provide more insights for designing excellent and reliable optical thermometers by employing Cr3+ activated luminescent materials.
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