THE SITE OCCUPANCIES FOR THE EXCESS MANGANESE ATOMS AND THE 3RD ELEMENT NIOBIUM IN THE INTERMETALLIC COMPOUND ZRMN2

The site occupancies for the stoichiometric excess of Mn atoms and the third element Nb in the hexagonal C14-Laves type ZrMn2 were studied b y investigating systematic changes of the lattice parameters and the b roadenings of diffracted X-ray profiles with the chemical compositions for ZrMnx (x=0.9-2.89) and Zr(Mn1-yNby)(x) (x=0.97-2.91, y=0.036-0.21 2) alloys. The excess Mn atoms in ZrMnx alloys (hypo-Zr) occupy the A sites in the hexagonal C14-Laves type AB(2) crystal. Nb atoms in Zr(Mn 1-yNby)(x) alloys (hyper-Zr) occupy the B sites. Nb atoms in Zr(Mn1-yN by)(x) alloys (hypo-Zr) are substituted for Mn atoms in the A sites un til Mn atoms in the A sites are exhausted. They turn to occupy the B s ites after Mn atoms in the A sites are exhausted.