Domain switching in ferroelectrics is at the heart of many functionalities, and the visualization of switching pathway is the key to understand the fundamental properties and to promote the applications of high-performance ferroelectrics. Here, we directly documented the multi-step domain switching in [110]-oriented 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-0.33PT) single crystals under a cycling electric field with the help of in situ polarized light microscopy. Based on the characteristic domain configuration analysis, we demonstrated that the 180° switching process was consisted of multi-step 60° switching. Such a multi-step 60° switching pathway resulted in a large negative strain and an internal electric field, which contributes to a large polarization fatigue rate under the alternating electric field. Our works may provide a window to study the domain switching process and its effect on polarization fatigue in relaxor-ferroelectric single crystals.

铁电体中的域切换是许多功能的核心，而切换路径的可视化是了解基本特性并促进高性能铁电体应用的关键。在这里，我们直接记录了在[110]取向的0.67Pb（Mg _1/3 Nb _2/3）O ₃ -0.33PbTiO ₃（PMN-0.33PT）单晶中的多步域切换，其中原位帮助偏光显微镜。基于特征域配置分析，我们证明了180°切换过程由多步60°切换组成。这种多步60°转换路径会产生较大的负应变和内部电场，从而在交变电场下会导致较大的极化疲劳率。我们的工作可能为研究畴弛豫过程及其对弛豫铁电单晶中极化疲劳的影响提供一个窗口。