Photoluminescence Spectra Correlations with Structural Distortion in Eu 3+ - and Ce 3+ -Doped Y 3 Al 5-2 x (Mg,Ge) x O 12 ( x = 0, 1, 2) Garnet Phosphors.

Garnet-type materials consisting of Y 3 Al 5-2 x (Mg,Ge) x O 12 ( x = 0, 1, 2), combined with Eu 3+ or Ce 3+ activator ions, were prepared by a solid-state method to determine the structural and optical correlations. The structure of Y 3 Al 5-2 x (Mg,Ge) x O 12 ( x = 1, 2) was determined to be a cubic unit cell (Ia-3d), which contains an 8-coordinated Y 3+ site with octahedral (Mg,Al)O 6 and tetrahedral (Al,Ge)O 4 polyhedra, using synchrotron powder X-ray diffraction. When Eu 3+ or Ce 3+ ions were substituted for the Y 3+ site in the Y 3 Al 5-2 x (Mg,Ge) x O 12 host lattices, the emission spectra showed a decrease in the magnetic dipole f - f Eu 3+ transition and a redshift of the d - f Ce 3+ transition, related to centrosymmetry and crystal field splitting, respectively. These changes were monitored according to the increase in Mg 2+ and Ge 4+ contents. The dodecahedral and octahedral edge sharing was identified as a key distortion factor for the structure-correlated luminescence in the Eu 3+ /Ce 3+ -doped Y 3 Al 5-2 x (Mg,Ge) x O 12 garnet phosphors.