Polytypes and Intergrowth of the Intermetallic Compounds Sm2Ni7

Intermetallic compounds in the Sm-Ni system whose compositions are near Sm2Ni7 have been studied by high-resolution electron microscopy. Four new polytypes of 4H, 5T, 9R and 12R, the intergrowth of Sm5Ni19 in between the matrix of Sm2Ni7, stacking faults and several defect structures are found in the specimens, and their structures are analysed by high-resolution lattice imaging method combined with electron diffraction.