Order-disorder phase transition and lattice parameter of Ni–Pt alloys

In this paper order-disorder phase transition of undoped Ni0.5Pt0.5 alloy and doped with Fe and Co with compositions Ni0.45Fe0.05Pt0.5 and Ni0.45Co0.05Pt0.5 respectively were studied by X-ray diffraction (XRD) method. It has been observed that Ni–Pt alloys undergo disorder-order transformation at high temperature from fcc (face centered cubic) structure to fct (face centered tetragonal) phase. Lattice parameters of the three disordered and three-ordered Ni–Pt and doped alloys were determined. Disordered state of Ni–Pt alloy shows fcc structure with lattice parameter of a = 3.7468 Å, while ordered one is fct having a = 3.8187 Å and c = 3.6028 Å with c/a ratio of 0.943. A slight increase of c/a ratio has been observed for Fe and Co doped alloys. The lattice parameters of the ordered fct phase of Ni0.45Fe0.05Pt0.5 and Ni0.45Co0.05Pt0.5 are a = 3.8141 Å, c = 3.6069 Å and a = 3.8174 Å, c = 3.6154 Å with c/a ratio of 0.945 and 0.947 respectively. Fe and Co doped Ni–Pt alloys has been found to be multiphased in contrast to the undoped counterpart. The corresponding N–R functions for each reflection planes have been reported as well