A new crystal structure of pure cobalt formed in ultrafine particles

Abstract

A long-period stacking structure of 9R, which has the stacking order ABC/BCA/CAB, has been found in ultrafine cobalt particles 20–500 nm in diameter. The structure seems to have resulted from the martensitic transformation of f.c.c. cobalt on cooling to room temperature. Electron microscopy reveals the existence of heavily faulted particles, the structure of which is presumed to be 9R.