Grain size effect on lattice of ni nanocrystals prepared through polyol method.

Nanocrystalline nickel powders were prepared with grain size 'd' in the range 40-100 nm diameters through polyol method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used for characterization. XRD of the prepared samples consistently matched with standard fcc structure of nickel without any impurity peak. Detailed analysis and calculations using Scherrer equation for (111) peak revealed systematic increase in line width and peak shifting towards lower diffraction 2theta angles with decrease in nickel to ethylene glycol mole ratio. Different values of d estimated from various peaks of each sample suggested associated microstrains in the nanograins. Values of d estimated from X-ray diffraction patterns were compared with those obtained from atomic force microscopy and scanning electron microscopy results, and discussed. Observed lattice expansion is explained, on the basis of a theoretical model of linear elasticity.