Preparation and optical properties of nanoscale MgAl2O4 powders doped with Co2+ ions

Co2+-doped MgAl2O4 nanocrystalline powders were prepared by co-precipitation method. The gels and/or calcined samples were characterized by means of thermogravimetry and differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectrum and near-infrared absorption spectrum. MgAl2O4 nanocrystals were produced by calcining the gel above 800 °C, with the crystallite size of 10-30 nm in the temperature range of 800-1100 °C. The influence of pH value of precipitant solution on the dispersing of powders was studied and the result showed that Co:MgAl2O4 nanocrystalline powders exhibited good dispersion when pH = 11. The absorption spectrum of Co2+-doped MgAl2O4 exhibited a broad absorption band in the wavelength range of 1200-1600 nm, which indicated that Co2+ ions substituted for the tetrahedrally coordinated Mg2+ ions in the MgAl2O4 lattice.