Orientation-dependent plasticity in microcompression of oxide single crystals

Micropillar compression (microcompression) is a promising technology for studying the intrinsic strength and plasticity of macroscopically brittle ceramics. However, their ductility limits at microscopic scale have rarely been investigated. This study digests the orientation dependence of the strength and ductility of various oxide single crystals with cubic structures (9.8-mol% Y₂O₃-stabilized ZrO₂, Y₂O₃, MgAl₂O₄, and SrTiO₃) using room-temperature microcompression, electron microscopy observation, and crystal plasticity finite element method simulation. The strength and ductility of these oxides exhibited remarkable orientation dependence. Specifically, the ZrO₂ [111] and SrTiO₃ [001] pillars demonstrated substantial ductility with no visible cracks, even at nominal strains of approximately 40%. The ductility may be attributed to mechanisms suppressing slip localization without causing dislocation interlocking. Multiple-slip activation was preferred across several slip modes of ZrO₂, Y₂O₃, and MgAl₂O₄, which was attributed to the forest-cutting interactions among dislocations of different slip systems. In contrast, the ductility of SrTiO₃ required the activation of a single slip, where slip localization was suppressed by the strain transfer associated with the formation of Lüders band. The relationship between ductility and slip activation may be influenced by the competition between the Peierls mechanism and dislocation–impurity interactions.