Synthesis of Ba1−xSrxYSi2O5N and discussion based on structure analysis and DFT calculation

Abstract

Cation substitution for inorganic solid materials is a practical approach to control their functions. Here, synthesis, structure analysis, density functional theory (DFT) calculation of novel oxynitrides Ba1−xSrxYSi2O5N, and investigation of their photoluminescence properties with Eu2+- or Ce3+-activator were conducted. Single crystal and powder X-ray analyses revealed that Ba1−xSrxYSi2O5N were formed at x ≤ 0.75 and they were isotypic while the synthesis of SrYSi2O5N (x = 1) was not achieved by any synthesis conditions examined. Based on phonon calculation, it was concluded that the synthesis of SrYSi2O5N with the isostructure to BaYSi2O5N was impossible due to the thermodynamical unstability. Substitution of Ba with Sr decreased the average bond length of AE-(O,N) (AE = Ba and Sr) and increased distortion of AE sites. On the other hand, coordination environments of Y sites were rarely affected by the substitution. As a result, redshift and broadening of emission spectra for Eu-doped samples were observed, whereas there was almost no spectral change in Ce-doped samples.