Growth and Characterization of Titanium Doped Spinel Crystals

MgAl₂O₄ (magnesium aluminates spinel, MAS) single crystals doped with titanium ions obtained by the Verneuil method were non-uniformly colored along of the growth crystallographic direction. The crystals were characterized measuring lattice parameter, optical absorption spectra and relative concentration of impurity atoms (Ti, Mn, Cr, and Fe) in different spots of grown Ti:MAS boule. There was observed the correlation of the intensity of absorption band at 800 nm to the relative concentration of iron supporting the identification of this band with charge transfer transition in complexes Ti⁴⁺+Fe²⁺ → Ti³⁺+Fe³⁺. The new resonant structure at the wavelength of 470 nm was found and tentatively identified with the Fano resonance in the complexes formed by lattice defects and impurity ions.