2011 Volume 52 Issue 3 Pages 374-379
This paper reports the results of structural study on the ordered phases formed in Pd-rich Pd-Mn alloys adopting X-ray powder diffraction method. Formations of the tetragonal D023-type Pd3Mn, orthorhombic Pd2Mn and orthorhombic Pd5Mn3 reported by previous researchers have been confirmed. Rietveld refinement of the diffraction data of the latter two phases has determined precisely the atomic parameters and revealed the significance of the shifts of atoms in Pd2Mn. It is shown that the L10-type phase extends to about 33 at% Mn at high temperatures and Pd2Mn and Pd5Mn3 form via two-step ordering from the L10-type phase. A revised phase diagram on the Pd-rich side has been proposed. Discussion is given on the stability of the relevant ordered phases by making calculation of the total energy by the density functional method.