Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 59: Computational Materials Modelling IX - Ferroelectrics
MM 59.1: Vortrag
Donnerstag, 3. April 2014, 15:45–16:00, IFW D
Ferroelastic Switching of Doped Zirconia – First-Principles Insights — •Christian Carbogno1,2, Carlos G. Levi1, Chris G. Van de Walle1, and Matthias Scheffler1,2 — 1Materials Department, University of California, Santa Barbara, USA — 2Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin
ZrO2 based ceramics play a pivotal role for thermal barrier coatings in gas and propulsion turbines. The phase stability required for these applications is typically achieved by Y-doping, which however also results in an undesirable degradation of toughness. Recently, high phase stability and toughness has been achieved by co-doping such Y-stabilized ZrO2 (YSZ) with Ti (TiYSZ) [1]. We use density-functional theory to investigate these effects by inspecting the underlying structural dynamics. Our calculations reveal that the minimum-energy path (MEP) for the tetragonal-to-cubic phase transformation differs significantly from the path discussed in literature [2]. We show that the correct MEP involves ferroelastic switches, i.e., the realignment of the tetragonality along a different cartesian direction. We inspect how (co-)dopants affect these ferroelastic switches, which are typically considered to be the primary toughening mechanism in these compounds [1]. Hence, our calculations shed light on the atomistic mechanisms that determine the dynamics and the high-temperature properties of YSZ and TiYSZ.
[1] T. A. Schaedler, O. Fabrichnaya, and C. G. Levi, J. Eur. Ceram. Soc. 28, 2509 (2008).
[2] S. Fabris, A. T. Paxton, and M. W. Finnis, Acta Materialia 50, 5171 (2002).