Uniform nanosized NiO particles were prepared by a chedrical coprecipitation usingNiCl2.6H2O as the starting material. The relationship between various annealing telnperaturesand grain size of NiO crystallite was investigated. Optical reflectivity spectra of Nanometer-sizedNiO powders at roonl temperature were studied. The results show that seven optical absorptionbands (P1. P2. P3. P4. P5. P6 and P7) with the peak energies of 3.30, 2.99, 2.78, 2.25,1.92, 1.72 and 1.07eV, respectively, are located on a continuous refiectivity background. P1.P2. P3 and P4 exhibit "blue shift", but P5. P6 and P7 present "red shift"in comparison withthat of single crystal NiO. The continuous reflectivity background increases rapidly with increasingthe annealing temperature from 500℃ to 600℃ to 700℃. The origins of P1 to P7 and thereasons of "blue shift", "red shift" and the increase of the reflectivity background with increasingthe annealing temperature have been analyzed in detail.
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