Broadband white luminescent phosphor Ba(Si7−xAlx)Liy(N10−x+yOx−y):Eu2+ with a high color rendering index for solid state lighting†
Abstract
Analysis of a mixture product from Ba3N2, Si3N4, AlN, Li3N, and EuN reveals a broadband white luminescent particle Ba(Si7−xAlx)Liy(N10−x+yOx−y):Eu2+. It shows a high color rendering index value of 90 despite being an Eu2+ only-doped material. The emission spectrum at a low temperature of −190 °C can be decomposed into three Gaussian profiles, indicating a crystal structure with three unique Eu coordination spheres. Single crystal XRD analysis shows that the single Ba site in Ba(Si7−xAlx)(N10−xOx) splits into three Ba sites. From the chemical analysis and bond valence sum map of the Li ion, we estimate that Li intrudes into the Ba(Si7−xAlx)(N10−xOx) lattice and shifts some Ba from its original position to two new Ba sites. This is a unique approach where a new phosphor is obtained by introducing a small cation into a known crystal structure.