Direct measurement of the concentration fluctuations in liquid Bi-Zn alloys

The e.m.f. method with a molten salt electrolyte was used to measure directly the composition gradient of the e.m.f. (i.e. (ΔE)/(Δx)) and hence the concentration fluctuations of liquid Bi-Zn alloys above the miscibility gap are determined. The concentration fluctuations are strong and above the values of an ideal solution. In the region of miscibility gap the concentration fluctuations increase strongly with decreasing temperature and the flat maximum tends to be more steep towards the critical composition. A simple model assuming the existence of polyatomic self associates in a demixing liquid alloy is used to describe the concentration fluctuations. Further, ΔE vs temperature variation is used to infer the temperature and the composition of the binodal. The temperature dependence of the atomic transport properties, such as diffusion, is also discussed in relation to the concentration fluctuations.