Samarium-cobalt 2:17 magnets: Identifying Sm n +1Co5 n a degree 1 phases stabilized by Zr

The complexities accompanying the interpretation of electron diffraction patterns in the extended Sm-Co alloy system are discussed. The many possibilities of confusing the prominent three phases of the homologous series Sm n +1Co5 n a degree 1 (n =2,3,4) with each other and with SmCo5 are highlighted, showing the limitations but also the power of this method. The observation of a diffraction pattern that is ostensibly the SmCo5 type does not preclude the possibility that it is actually due to a compound from the series Sm n +1Co5 n a degree 1.