Crystal field splitting and symmetry of Ce3+ polyhedra in oxide crystals

Single crystals of Ce3+-doped oxides Ca2Al2SiO7 (CASM), CaYAl3O7 (CYAM) and CaYAlO4 (CYAP) have been grown in inert and reducing atmospheres, with int ent of studying the effects of symmetry and ligand cordination on the dopan t energy levels. The optical absorption spectra of Ce3+ in these crystals a t most consist of five overlapping bands. The luminescence is also a broad band due to strong electron-phonon interaction in the 5d excited state. The luminescence bands for CASM, CYAM and CYAP are intermediate between GdAlO3 (GAP) and Y3Al5O12 (YAG). The energies of the lowest absorption band and t he luminescence band decrease in order of GAP, CASM, CYAM, CYAP, and YAG. T his trend may be explained by lowering symmetry and reducing size of the an ion-coordinate polyhedra of Ce3+ in these crystals.