Optical absorption of Co2+ in gel-derived aluminosilicate glass-ceramics

Pure and Co2+-doped aluminosilicate gels were prepared by the sol-gel method from two different aluminum salts, aluminum-iso-propoxide and aluminum nitrate, and heat-treated at 40-1200 °C. Visible and near-infrared (NIR) absorption spectra of the heated samples were studied. When the heat-treatment temperature was 1100 °C, Co2+-doped aluminosilicate samples, obtained by using aluminum-iso-propoxide, crystallized to Al2O3 nanocrystals and exhibited a broad absorption band in the range of 1200-1600 nm, which is characteristic of tetrahedral Co2+ ions in crystals. The existence of the broad absorption band has allowed us to consider this kind of material as possible candidate for passive Q-switched materials in the NIR region. While the sample prepared from aluminum nitrate was amorphous when heated to 1200 °C.