Effect of Ca2+ codoping on the Eu2+ luminescence properties in the Sr2Si5N8 host lattice: a theoretical approach

Here we report a theoretical analysis of the luminescence properties of Sr2Si5N8 host lattices codoped with Ca2+ and Eu2+. These systems have been first synthesized by Li et al. [J. Solid State Chem., 2008, 181, 515], who have found that Ca2+ doping provokes a red-shifting of the emission peak of Eu2+, from 620 nm to 643 nm. However, the mechanism that drives this shift is still unclear from experimental data. Based on density functional theory and ligand field analysis, we study the structure, stability, and emission properties of Eu2+ embedded in the (Sr1-xCax)(2)Si5N8 host lattice. Our results provide a full explanation of the experimental data and the methodology could constitute a valuable tool for the design of phosphors with tunable emission spectra.