Effect of gamma-irradiation on some structural characteristics of NiO

Pure NiO specimens were prepared by the thermal decomposition of pure basic nickel carbonate in air at 400 and 600°C. The obtained solids were exposed to different doses of γ-irradiation ranging between 10–80 Mrad. The change in residual microstrain, lattice parameter and crystallite size due to the irradiation process were investigated by X-ray diffraction analyses.The results revealed that γ-irradiation effected important changes in the structural characteristics of NiO lattice. No detectable change was observed for the crystalline size of NiO-400°C; however, the crystallite size of NiO-600°C decreased by increasing the dose up to 20 Mrad and increased at higher doses but still remaining smaller than that measured for the unirradiated specimen.The lattice parameters of NiO preheated at 400 or 600°C were found to increase as a function of the dose. These results were attributed to progressive removal of Ni³⁺ ions acting as lattice defects in NiO solid.The microstrains in NiO specimens precalcined either at 400 or 600°C were found to decrease progressively by increasing the dose falling to minimum values at doses of 40 and 80 Mrad for the solids preheated at 600 and 400°C, respectively. The augmentation of the exposure dose above 40 Mrad for NiO-600°C resulted in an increase in microstrain which, however, remained always smaller than those found for the unirradiated solid. The strain-relief in NiO-600°C due to γ-irradiation took place, mainly, via splitting of its crystallites. On the other hand, the progressive removal of lattice defects (Ni³⁺ ions) due to the irradiation process might account for the observed strain-relief in NiO-400°C.