Local structure of NiTi nanocrystals studied by EXAFS and XRD

A series of NiTi nanocrystals with different annealing temperatures, prepared by sputtering method, were investigated by extended x-ray absorption fine structure (EXAFS) and x-ray diffraction. It was found that the structure of nano-phase powder is different from bulk NiTi alloy with bcc structure as target materials. When increasing the annealing temperature, a small fraction of the (Ni, Ti) type nanocrystal with the hexagonal structure was presented except target materials and Ni, and it is atomic occupation in random. Finally there were four Ti and two Ni atoms around central Ni atoms, and the bond length of Ni-Ti and Ni-Ni were 0.2462nm and 0.2585nm at 800 degreesC annealed.