Search

The EXAFS measurements on polycrystalline and nanocrystalline Co samples were performed at the PULS synchrotron radiation facility. In contrast to the conventional EXAFS data analysis using an inverse Fourier transformation we have applied a modified regularization algorithm in order to determine the pair correlation function (PCF) by solving the integral EXAFS equation. The PCF for a polycrystalline sample indicates several separate peaks located on true interatomic distances. For nanocrystalline cobalt we obtain a reduction of the first coordination number (N=6.4 at.). The results obtained are discussed.

An EXAFS study of the local environment of nanocrystalline cobalt is presented. In order to determine the pair correlation function (PCF) by solving the integral equation we applied a modified regularization algorithm. For nano-Co we obtain an enhanced reduction of the first coordination number (N = 6.4 atoms). The difference of nano- and poly-EXAFS (with some weight coefficient) spectra yields a weak signal, originated from the atoms in the boundary layer of crystalline grains (not only on the surface of grains). The grain boundary component PCF indicates a small symmetric peak with interatomic distance r = 2.52 A and coordination number N = 4 atoms. The obtained results are discussed.

An EXAFS study of the local environment of nano-crystalline cobalt is presented. For nano-Co we obtain a reduction of the first coordination number (N = 6, 4at.). The difference of nano- and poly- EXAFS (with some weight coefficient) spectra yields a weak signal, originating from atoms in the boundary layer of crystalline grains (not only in the surface of grains). The pair correlation function (PCF) of the grain boundary component indicates a small symmetric peak with interatomic distance r = 2.52 A and coordination number N = 4 at. The results obtained are discussed.