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(Si_7−xAl_x)Li_y(N_10−x+yO_x−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(Si_7−xAl_x)(N_10−xO_x) 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(Si_7−xAl_x)(N_10−xO_x) 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.