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Abstract
The interaction of Ti, Mg, OH− and O2- ions in LiF have been studied. Ti usually enters the lattice as Ti4+, but in samples grown in inert atmosphere from a vitreous carbon tube another charge state (most probably Ti3+) has also been found. In “as-grown” LiF (inert) crystals Ti3+ ions appear to be in aggregated form giving rise to a broad absorption band at ∼660 nm. Quenching the crystal the broad band decreases simultaneously with the appearance of an ESR spectrum indicating the presence of some paramagnetic Ti3+ containing species.
IR bands at 3662 and 3525 cm−1 in air grown LiF:Ti and LiF:Mg, Ti, respectively were attributed to Ti-OH complexes. Ionic conductivity measurements indicate that the extra charges of Ti ions in all investigated samples are compensated to some extent by cation vacancies.
The evident differences in optical absorption and ESR results suggest that the coordinations of the Ti ions in LiF:Ti are different from those in double-doped crystals.