Powder diffraction refinement of the Co_2Al_5 structure

摘要

The structure of Co_2Al_5(hP28, pb_3/mmc) was refined by means of Rietveld method. The shortest Co-Al distance amounts 2.338 A. Co_2Al_5 shows a homogeneity range between Co_29Al_71 and Co_27.5Al_72.5 at 1125 K. The concentration dependence of lattice parameters was also measured. The Axial ratio c/a increases with increasing mole fraction of aluminum.