A novel KSrScSi2O7:xCr silicate phosphor, luminescence/chromaticity, and applications in NIR pc-LED and stable green ceramic pigments

The emission wavelength of current near-infrared phosphors activated by Cr 3+ is generally smaller than 900 nm in near-infrared (NIR) I region, and it is extremely challenging and is of great practical significance to realize emission towards NIR-II region. In this study, a novel Cr 3+ excited KSrScSi 2 O 7 silicate broad-band phosphor was prepared using the traditional solid-state method. Cr 3+ resides in a weak crystal field in the KSrScSi 2 O 7 lattice and exhibits broad-band near-infrared emission at 984 nm, longer than those of most Cr 3+ activated phosphors, under 493 nm blue light excitation. This is due to the strong charge polarization caused by the unique local coordination environment of the silicate matrix, which leads to a reduction in the crystal field splitting energy of the [ScO 6 ] octahedron where Cr 3+ is located and the downward shift of the 4 T 2 energy level. The optimal doping concentration of Cr 3+ is found to be 2 mol%, and the quenching mechanism is dipole-dipole interaction. Compared to the phosphors with similar emission wavelengths ( λ em > 900 nm), KSrScSi 2 O 7 :Cr 3+ demonstrates outstanding advantages in various aspects of luminescent performance. The fabricated phosphor-converted light-emitting diode (pc-LED) is shown to have the potential for night vision and non-invasive imaging. Novel application of KSrScSi 2 O 7 : x Cr 3+ as stable green ceramic pigments is also explored. The KSrScSi 2 O 7 : x Cr 3+ powders show a bright yellowish green appearance, and the KSrScSi 2 O 7 :0.02Cr 3+ typical composition has chromaticity values of L* = 82.73, a* = –8.53, b* = 7.97. Remarkably, the glazing samples using KSrScSi 2 O 7 : x Cr 3+ as pigments well retain the bright color after 1200 °C sintering in different atmospheres. Therefore, multi-functional applications of KSrScSi 2 O 7 : x Cr 3+ for near-infrared spectroscopy and as ceramic pigments are achieved in this work.