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CaYA104 crystals codoped with V + and Mg + ions have been grown in an inert atmosphere. EPR measurements reveal that V + ions in CaYA104 occupy orthorhombic symmetry sites. The optical-absorption spectrum comprises two intense bands with peaks at 330 and 430 nm, together with a weak band around 500 nm. Excitation in the 500-nm band produces a broad luminescence band with a peak at 690 nm. The radiative center associated with these spectra is assigned to V +(3d ) ions. The peak wavelength of the luminescence band shifts to longer wavelengths with increasing excitation wavelengths in the 500-nm absorption band, an efFect associated with the inhomogeneous broadening of the luminescence band caused by random distribution of Ca + and Y + ions in the disordered CaYA104 lattice.

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Five absorption bands with peaks at 210 nm, 246 nm, 284 nm, 296 nm, and 368 nm were observed at room temperature for Ce-doped CaYAlO 4 (CYA) crystals grown in a reducing atmosphere. Excitation at wavelengths below ∼400 nm of Ce:CYA crystals produces a broad luminescence band with a peak at ∼485 nm. The excitation spectrum of the luminescence detected at a fixed wavelength of 485 nm is very similar to the absorption spectrum. The ultraviolet absorption and visible luminescence are due to the 4f 1 ↔ 5d 1 transitions of Ce 3+ ions in CYA. The linear dependence of the luminescence peak energy on the excitation energy shows that the luminescence is inhomogeneously broadened by a random distribution of Ca 2+ and Y 3+ ions in the disordered CYA lattice.

The x-ray diffraction patterns for Ce 3+ -doped BaMgF 4 (BMF) crystals suggest the existence of superlattice structure. The superlattice model is consistent with the characterization of the 4f 1 ground state of Ce 3+ as a probe ion using the electron spin-resonance (ESR) technique. The distinct Ce 3+ luminescence spectra with different peak energies and lifetimes also support the superlattice model. Although the detailed superlattice structure could not be analysed using the diffraction spots, a model has been proposed, taking into account the eight Ce 3+ polyhedra with different anion coordinations in the unit cell of the BMF crystal obtained from the ESR experiments.