Photoluminescence Spectra Correlations with Structural Distortion in Eu3+- and Ce3+-Doped Y3Al5-2x(Mg,Ge)xO12 (x=0, 1, 2) Garnet Phosphors

Abstract

Garnet-type materials consisting of Y3Al5-2x(Mg,Ge)(x)O-12 (x = 0, 1, 2), combined with Eu3+ or Ce3+ activator ions, were prepared by a solid-state method to determine the structural and optical correlations. The structure of Y3Al5-2x(Mg,Ge)(x)O-12 (x = 1, 2) was determined to be a cubic unit cell (Ia-3d), which contains an 8-coordinated Y3+ site with octahedral (Mg,Al)O-6 and tetrahedral (Al,Ge)O-4 polyhedra, using synchrotron powder X-ray diffraction. When Eu3+ or Ce3+ ions were substituted for the Y3+ site in the Y3Al5-2x(Mg,Ge)(x)O-12 host lattices, the emission spectra showed a decrease in the magnetic dipole f-f Eu3+ transition and a redshift of the d-f Ce3+ transition, related to centrosymmetry and crystal field splitting, respectively. These changes were monitored according to the increase in Mg2+ and Ge4+ contents. The dodecahedral and octahedral edge sharing was identified as a key distortion factor for the structure-correlated luminescence in the Eu3+/Ce3+-doped Y3Al5-2x(Mg,Ge)(x)O-12 garnet phosphors.