Electrical Resistivity of Nanocrystalline Ni-P Alloys

Nanometer-size polycrystalline Ni—P alloys that contain two phases of Ni3P and Ni were synthesized by the crystalline process from an amorphous Ni80P20 alloy that had been isothermally annealed at certain temperatures. Nanocrystalline Ni—P samples with different mean grain sizes (10 to 100 nm) were prepared by changing the annealing temperature and time. The electrical resistivity of these nanocrystalline ribbon samples was measured with the conventional dc four-probe method from room temperature to liquid nitrogen temperature. The resistivities were linearly proportional to the absolute temperature before the onset of grain growth at about 613 K. The temperature coefficients of resistivity varied slightly with the mean grain sizes; the residual resistivities decreased significantly (from 214.1 to 65.5 μΩ• cm) as the grain size increased from 11 to 102 nm. The dependence of the residual resistivity on grain size can be reasonably correlated to the relationship between the interface volume fraction and growth size. These results indicate that the resistivity of the nanocrystalline materials is strongly dependent on the interface characteristics.