Dresden 2014 – scientific programme

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DS: Fachverband Dünne Schichten

DS 40: Focus Session: Resistive Switching by Redox and Phase Change Phenomena VII (Optical properties and theory of PC materials)

DS 40.5: Talk

Thursday, April 3, 2014, 12:30–12:45, CHE 89

Structural phase transitions in thin films under elastic and microstructural constraints — •Stefan Wagner and Astrid Pundt — Institut für Materialphysik, Universität Göttingen

Palladium hydrogen (PdH) thin films are used as a model system to investigate the impact of elastic and microstructural constraints on structural phase transitions. Mechanical stress arises both from thin film clamping on the substrate and at coherent interfaces in phase mixtures. It changes chemical potentials, modifying phase stabilities regarding phase boundaries and enthalpies of formation. Mechanical stress is superimposed by microstructural constraints, channeling stress relaxation mechanisms such as the formation of misfit dislocations.

In this paper hydrogen absorption and hydride formation in PdH thin films with different microstructure and clamping conditions are investigated [1]. Hydrogen solubilities and phase stabilities are quantitatively related to the hydrogens' chemical potential by in-situ XRD as well as stress and electromotive force (EMF) measurement [2]. They differ for films with coherent interfaces and films where stress relaxation is possible. [1] S. Wagner, A. Pundt, Acta Mat. 59 (2011) 1862. [2] S. Wagner, M. Moser, A. Pundt et al., Int. J. Hydr. Energy 38 (2013) 13822.