Effect of Ca(2+) codoping on the Eu(2+) 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 Ca(2+) and Eu(2+). These systems have been first synthesized by Li et al. [J. Solid State Chem., 2008, 181, 515], who have found that Ca(2+) doping provokes a red-shifting of the emission peak of Eu(2+), 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 Eu(2+) embedded in the (Sr1-xCax)2Si5N8 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.