Optical Absorption and Photoluminescence Spectra of Ce-doped SrMgF4 Polycrystalline with Superlattice Structure

Rare-earth (RE) ions doped perovskite-related fluorides are candidates for tunable optical materials. In this work, SrMgF4: xCe (x=0, 0.007, 0.013 and 0.035, in mole) powders were synthesized by a precipitation method. X-ray diffraction (XRD) patterns indicate that the obtained phosphors possess monoclinic superstructures. Electrovalence analysis confirms the existence of Ce3+/Ce4+ mixed valence. Two distinct fluorescence bands B and C were observed with different excitation wavelengths in the ultraviolet (UV) light region. Energy levels were modified strongly by the crystal field derived from monoclinic superstructures when the symmetry of Ce3+-polyhedra changed from high- to low- symmetry.