Regensburg 2019 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 20: Poster session II

MM 20.7: Poster

Dienstag, 2. April 2019, 18:30–20:00, Poster C

determination of the miscibility gap of Pt-Pd using Atom Probe Tomography — •Yoonhee Lee and Guido Schmitz — Heisenberstr. 3, 70569 Stuttgart

Understanding the thermodynamics of alloy system is fundamental and a prerequisite to interpret the properties of the materials. So, no surprise that of most binary metallic system the phase diagrams were already well evaluated. Nevertheless, in some cases required data are missing, which holds especially for miscibility gaps at low temperature. A miscibility gap is suggested for Pt-Pd, an important alloy system essential for catalysis. Even though there were many efforts to prove the miscibility gap since Raub [1] have first claimed it with a critical temperature of approximately 770°C, still the gap remains as a dashed unclear line in the published phase diagrams [2].

In this work, we try to overcome the lack of information by applying Atom Probe Tomography (APT) to thin film structures needing only short diffusion length to establish equilibrium. APT is a cutting-edge technology, which can achieve an outstanding three-dimensional spatial resolution. Thus, it enables the study of atomic diffusion on a (sub-)nanometer length scale. Pt and Pd multilayers are deposited via ion beam sputtering and annealed at different temperatures to approach equilibrium. Then, needle-shaped samples are prepared by FIB lift-out and measured in APT. The experimentally determined miscibility gap is presented in comparison to literature data.

[1] *E. Raub, Journal of the Less-Common Meterials, vol. 1, pp. 3-18, 1959. [2] *T. Massalski, Binary Alloy Phase Diagrams, 1990.