A revision of the Ni-Zn phase diagram based on vapor-solid diffusion experiments

The technique of vapor-solid diffusion couples was systematically studied for its potential in phase diagram investigation using the well-established Ni-Zn system which is highly suitable for this purpose due to the high vapor pressure difference of the two constituents. More than 50 samples synthesized by direct vapor-solid reaction, varying the parameters temperature, time and overall system composition, were investigated by SEM/EDX focusing on diffusion profile line-scans. Supporting powder-XRD and DTA experiments were performed as well. Based on these experimental results, significant changes to the currently accepted Ni-Zn phase diagram, specifically concerning the β, β₁, and γ phase fields, are proposed. Furthermore, a relatively simple experimental procedure to prepare vapor-solid diffusion experiments is introduced and its application in phase diagram investigation is discussed in detail.