Structural effect of Zr substitution in the Sm2Co17 phase

In the Sm-Co-Zr system, a hexagonal Sm2Co17 structure is observed in the isothermal section at 1150 degrees C. Recent investigations have shown that only rhombohedral Sm2Co17 is stable in the Sm-Co binary system. X-ray patterns of samples annealed up to 1325 degrees C were indexed with the 2/17 R structure. The hexagonal structure is not a disordered form of the rhombohedral Sm2Co17 phase. It is obtained by deformation of the SmCo5 structure through the disordered SmCo7 structure. In this work, the crystal structure of this (Sm+Zr)(2)Co-17 compound has been determined and its stabilisation is discussed. (C) 1997 Elsevier Science S.A.