VARIATION IN LATTICE-PARAMETERS WITH GRAIN-SIZE OF A NANOPHASE NI3P COMPOUND

Nanocrystalline Ni-P alloy samples consisting of the compound Ni3P and Ni solution with different grain sizes were synthesized by crystalliz ation of the amorphous alloy. The lattice parameters of the Ni3P nanop hases with grain sizes ranging from 80 to 6.0 nm were measured by X-ra y diffraction. It was found that for the nanometer-sized Ni3P phase, t he lattice parameter a is always larger and c is smaller than the equi librium values a0 and a0, of the perfect crystal lattice respectively. With a reduction in the grain size, the value of a increases and c de creases, resulting in more significant lattice distortion. The origin of such lattice distortion was analyzed according to the thermodynamic state of the nanometer-sized crystallites.