Structure and redshift of Ce3+ emission in anisotropically expanded garnet phosphor MgY2Al4SiO12:Ce3+

To achieve a redshift of the Ce3+ emission, an overall compression of a garnet phosphor with anisotropic expansion of the local environment for the activator ion Ce3+ was designed, by the strategy of incorporating the small cation Mg2+ into the dodecahedral Y3+ site. The successful substitution of Mg2+ in the dodecahedral Y3+ site in the novel garnet phosphor MgY2Al4SiO12:Ce3+ was confirmed by the Rietveld refinements of XRD data, TEM and XPS results. The emission of MgY1.94Al4SiO12:0.06Ce(3+) ranges from 500 nm to 750 nm with the maximum being at 568 nm, which means that the expected redshift is realized, comparing with the commercial phosphor YAG:Ce3+. Furthermore, an anisotropic expansion mechanism, with a comprehensive view of crystal field splitting and the dynamic aspect factor of the Stokes shift, was proposed to interpret such a redshift, based on the bond length variation and the crystal field splitting data versus those of the counter phosphor Y3Al3MgSiO12:Ce3+ and YAG:Ce3+. The anisotropic expansion from cation substitution could serve as a general strategy to design new phosphors for high colour rendering index white LED lamps.