Electric field gradients in nanoparticles of HfAl2 and HfAl3 intermetallic compounds

Perturbed angular correlation (PAC) method was applied to study the electric field gradients in nanopowders of the HfAl2 and HfAl3 intermetallic compounds, obtained via mechanical alloying or after ball milling of the thermally alloyed compound. The influence of the ball milling procedure on the experimentally obtained hyperfine interaction parameters was determined. A strong dependence of the PAC pattern on the milling time was evidenced and attributed to the structural disorder. The thickness of the outer damaged part of the grains depends on the crystallographic structure of the milled material. In HfAl3 sample the influence of the milling procedure on the phase transformation was observed.