Luminescence Matching with the Sensitivity Curve of the Human Eye: Optical Ceramics Mg8-xMx(BN2)(2)N-4 with M = Al (x=2) and M = Si (x=1)

Compounds Mg8–xMx(BN2)2N4 were prepared by solid-state reaction of MgCl2, Li3(BN2), and AlN for M = Al, and of Mg3N2, BN, and Si3N4 for M = Si. Their crystal structures were refined from powder X-ray diffraction data with the space group Rm for M = Al, Si, and P21/c for M = Si. The structures of Mg8–xMx(BN2)2N4 are characterized by layered arrangements of wurtzite-related block layers alternating with a layer of di-nitridoborate ions along the c-axis direction. Cations in each structure are surrounded tetrahedrally by nitride and di-nitridoborate ions. Europium(II)-doped powders of Mg8–xMx(BN2)2N4 show exceptional broad band emissions in the visible region of the spectrum, on excitation with UV radiation at λex = 320 nm.