First-principles calculations of 4f–5d optical absorption spectra in BaMgAl10O17:Eu

In the well-known blue phosphor, BaMgAl10O17:Eu (BAM:Eu), Eu ions doped as the emission centers are generally considered to occupy at least three different sites; Beevers–Ross (BR), anti-Beevers–Ross (aBR) and mid-oxygen (mO) sites. However, among them, the most dominant site of the Eu2+ ions has not been identified yet. Moreover, although an additional absorption band at about 195 nm was recently observed by the excitation spectra of the low-temperature samples with more than 3 at% Eu concentrations, its origin has not been clarified yet. In order to clarify the origin of this additional band and the most dominant site, we have performed first-principles calculations of 4f –5d absorption spectra of three emission centers of BAM:Eu based on the recently developed relativistic configuration-interaction calculation method. The results indicate that this additional band originates from Eu2+ ions in the mO site and that the most dominant site is the aBR site.