Near-Infrared Luminescent Transparent Glass-Ceramic Containing Ba_2–<i>x</i>Sr_<i>x</i>NaNb₅O₁₅ Solid-Solution Nanocrystals with Wavelength Tunability

Near-infrared (NIR) light sources play a significant role in detection and therapies in healthcare, agriculture, and other fields for their outstanding ability of tissue penetration, excellent safety features, and useful bandwidth that match well with the vibration of chemical bonds. NIR phosphor-converted light-emitting diode (NIR pc-LED) devices are considered to be one of the most promising NIR light sources due to their unique advantages, including tunable wavelength, high efficiency, long life, low cost, and compact size. Compared to traditional resin-based casting technology, which has shortcomings such as complicated packaging process, poor thermal conductivity, and aging of plastic materials, transparent oxide glass-ceramics (GCs) have excellent optoelectronic properties, high physical and chemical stability, simple manufacturing processes, etc. Here, we report the synthesis of a series of Cr³⁺-doped Ba_2-<i>x</i>Sr_<i>x</i>NaNb₅O₁₅ nanocrystals embedded within GCs, which exhibit an ultrabroadband NIR emission covering 600 ∼ 1500 nm under 460 nm blue light excitation, by a two-stage heating-quenching and recrystallization method. It was noticed that as Ba²⁺ ions in the matrix were increasingly replaced by Sr²⁺ ions, the peak of the corresponding NIR emission of the GCs continuously shifted from ∼823 to 855 nm, and a photoluminescence quantum yield of ∼39.13% was achieved with the GCs NIR phosphor with an optimal composition. Mechanistic studies showed that the emission originates from the ⁴T₂ → ⁴A₂ spin-allowed transition of Cr³⁺ ions. NIR pc-LED light source devices were prepared from the optimized GCs and blue light LED chips, and their potential applications in night-vision imaging and nondestructive testing were demonstrated. Our study provides an innovative approach for the design of materials of continuous solid solution transparent oxide GCs with tunable wavelengths and their applications.