Ferroelectric materials are widely used in energy applications due to their field-driven multiferroic properties. The stress-induced phase transformation plays an important role in the functionality over repeated and consecutive operation cycles, especially at the micro/nanoscales. Here we report a systematic in-situ uniaxial compression tests on cuboidal Barium titanate (BaTiO) nanopillars with size varying from 100 nm to 3000 nm, by which we explore the stress-induced transformation and its interplay with plastic deformation. We confirm the superelasticity achieved in pillars by martensitic phase transformation from tetragonal to orthorhombic. There exists a critical size, 330 nm, for the yield stress. Above 330 nm, martensitic phase transformation aids slip along the plane with a low Schmid factor, in turn, the pseudo-compatible twins form within the shear band. The scaling exponent of size-dependent yield strength is found to be exactly 1. For nanopillars smaller than 330 nm, no twins form, only slips with large Schmid factors are activated, and size effect vanishes. All pillars with sizes from 100 nm to 300 nm achieve the theoretical yield limit around 9 GPa. Our experimental results uncover the interplay between twins and slips in BaTiO nanopillars, which pave the way for the optimization of microstructure design of ferroelectric materials for microelectronic applications at small scales.

中文翻译：

---

相变铁电纳米柱的孪生、滑移和尺寸效应


铁电材料由于其场驱动的多铁性而广泛应用于能源应用。应力引起的相变在重复和连续操作周期的功能中发挥着重要作用，特别是在微米/纳米尺度上。在这里，我们报告了对尺寸从 100 nm 到 3000 nm 的立方体钛酸钡 (BaTiO) 纳米柱进行的系统原位单轴压缩试验，通过该试验我们探索了应力诱导的转变及其与塑性变形的相互作用。我们确认了通过从四方相到正​​交相的马氏体相变在柱中实现的超弹性。屈服应力存在临界尺寸 330 nm。在 330 nm 以上，马氏体相变有助于沿着低施密特因子的平面滑移，进而在剪切带内形成伪相容孪晶。发现尺寸相关屈服强度的比例指数恰好为 1。对于小于 330 nm 的纳米柱，不会形成孪晶，只有具有大施密德因子的滑移被激活，尺寸效应消失。所有尺寸从 100 nm 到 300 nm 的柱子均达到 9 GPa 左右的理论屈服极限。我们的实验结果揭示了 BaTiO 纳米柱中孪晶和滑移之间的相互作用，这为小尺度微电子应用的铁电材料微观结构设计的优化铺平了道路。