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M: Metallphysik

M 22: Mechanische Eigenschaften III

M 22.2: Vortrag

Dienstag, 25. März 2003, 15:00–15:15, IFW B

Can the kink-pair theory apply for the flow stress of strontiumtitanate at high temperatures ? — •Dieter Brunner — Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart

SrTiO₃ single crystals with <001> compression axis exhibit a strong temperature and strain-rate dependence of the critical shear stress at high temperatures (1300 to 1800 K). Besides, the activation volume is be smaller than 10 b³ (b=Burgers vector). This suggests a rate-controlling process comparable with the kink-pair formation in dislocations with non-planar dislocation cores. The application of the kink-pair theory gives values for a Peierls stress (4.6 GPa), kink-pair energy 2H_k (6.4 eV), and for the Peierls valley distance a (3.9 nm) which value compares with the lattice constant a₀. This would suggest a fundamental step of kink-pair formation in <001> direction but due to the <001> compression direction {001}<001> slip systems are ruled out. As dislocations with b=a₀ <110> were detected to govern the deformation processes [1] other slip systems as, e.g., {110} <110> can apply. This is discussed in terms of climb dissociation and new observations of dislocation cores in SrTiO₃ [2]. The talk is given in German.

[1] S. Taeri, PhD Thesis Uni Stuttgart 2002; Z. Zhang et al., submitted to Phys. Rev. B