Electrical Resistivity, Thermoelectric Power, and X-Ray Interference Function of Amorphous Ni-Pt-P Alloys

Amorphous alloys having the composition ${\left({\mathrm{Ni}}_x{\mathrm{Pt}}_{1-x}\right)}_{0.75}{\mathrm{P}}_{0.25}$, where $0.20\le x\le 0.60$, were obtained by rapid quenching from the liquid state. X-ray diffraction measurements indicate a high degree of structural disorder in these alloys and an atomic configuration closely similar to that in liquid metals. At room temperature, the electrical resistivity $\rho$ of these alloys lies between 160-185 μΩ cm, and the absolute thermoelectric power $S$ between 1.9-2.5 μV/°K. On increasing the temperature from 4.2 to 420 °K, up to which the amorphous alloys are stable, the resistivity of the alloy with $x=0.20\mathrm{}$ decreases by about 2%; the value of $\frac{d\rho }{\mathrm{dT}}$ progressively increases with increasing Ni content, becoming positive at $0.50<x<\mathrm{}0.60\mathrm{}$. In the range 80-300 °K, the $\frac{\mathrm{dS}}{\mathrm{dT}}$ of all alloys lies between 5-8×${10}^{-3\mathrm{}}$ μV${\mathrm{deg}}^{-2\mathrm{}}$. The electrical behavior of these alloys may be treated in terms of electron scattering in disordered structures assuming the nearly free-electron model, in a manner analogous to Ziman's theory of electronic transport in liquid metals. The $\frac{d\rho }{\mathrm{dT}}$ of these alloys is then qualitatively explained in terms of the temperature and composition dependence of the x-ray interference function $a\left(K\right)\mathrm{}$, assuming an average number of ∼1.3 conduction electrons per atom in these alloys. For the alloy with $x=0.20\mathrm{}$, this implies a Fermi energy of 6.9 eV which corresponds to the position of the first peak in $a\left(K\right)\mathrm{}$. The thermoelectric-power results lead to the conclusion that the "average" form factor for scattering of electrons decreases with increasing Ni/Pt ratio.