Dislocation-based high-temperature plasticity of polycrystalline perovskite SrTiO3

Abstract

Dislocation networks have been demonstrated to substantially enhance functional properties. As-sintered samples are virtually devoid of dislocations, new innovative techniques for introducing sufficiently high dislocation densities into polycrystalline ceramics are needed. While dislocation-based plasticity at high temperatures has been demonstrated for a large range of ceramic single crystals, plasticity in polycrystals is much less understood. Here, we demonstrate plastic strains in excess of several % based on dislocation motion in polycrystalline SrTiO3 at ≈ 1100 °C with 3.9 µm grain size. Ultra-high voltage electron microscopy reveals an associated increase in dislocation density by three orders of magnitude. Achievable strain rates are comparable to creep-based mechanisms and much less sensitive to applied stress than observed for metals. A specialized testing protocol allows quantification of the deformability via stress exponent, activation volume and activation enthalpy giving additional quantification. In conjunction with TEM images, the mechanical data gives insight into the underlying mechanisms.