粒子径および組成を制御することによるユビキタス物質の高機能化 : LaTiO2N 系酸窒化物の光学特性の制御

Some Perovskite-type LaTiO2+xN1-x with anion nonstoichiometry were prepared by heating
an oxide precursor under ammonia atmosphere and successively annealed under diluted
ammonia. Increasing O/N ratio enhances the optical bandgap of the oxynitrides. A series
of perovskite-type LaTiO2N materials with compositions a slightly deviated from the
stoichiometric metal composition was also prepared. Increasing Ti/La ratio in
La1-xTi1+xTiO2N results in deterioration of reflectivity in the longer wavelength region above
the absorption edge. A substitution of La by Sr was effective in the enhancement of
reflectivity there. Though the increase of O/N ratio in the LaTiO2+xN1-x series was found to
cause oxidation of titanium by means of XPS spectroscopy, the valence state of titanium did
not change in either the La1-xTi1+xO2N or the La1-xSrxTiO2N series. The increase in Ti/La
ratio in the La1-xTi1+xO2N brought the grain/particle growth, which seemed to result in the
deterioration of reflectivity.