Luminescence Matching with the Sensitivity Curve of the Human Eye: Optical Ceramics Mg 8– x M x (BN 2 ) 2 N 4 with M = Al ( x = 2) and M = Si ( x = 1)

Compounds Mg 8– x M x (BN 2 ) 2 N 4 were prepared by solid‐state reaction of MgCl 2 , Li 3 (BN 2 ), and AlN for M = Al, and of Mg 3 N 2 , BN, and Si 3 N 4 for M = Si. Their crystal structures were refined from powder X‐ray diffraction data with the space group R $\bar {3}$ m for M = Al, Si, and P2 1 / c for M = Si. The structures of Mg 8– x M x (BN 2 ) 2 N 4 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 Mg 8– x M x (BN 2 ) 2 N 4 show exceptional broad band emissions in the visible region of the spectrum, on excitation with UV radiation at λ ex = 320 nm.