Ferroelectric degradation, the failure of polarization reversal under cyclic electric loading, hinders the application of ferroelectrics in reliable devices. While space charges are implicated, the underlying physics remains unclear. Using in-situ biasing transmission electron microscopy, this study reveals charge accumulation at domain walls as the primary cause of forming less responsive *c* domains. The rapid growth of these frozen *c* domains leads to degradation. This discovery provides insights into ferroelectric degradation in nanodevices and clarifies the role of injected charges in polarization reversal.

Qianwei Huang, Zibin Chen, Matthew J. Cabral, Feifei Wang, Shujun Zhang, Fei Li, Yulan Li, Simon P. Ringer, Haosu Luo, Yiu-Wing Mai, Xiaozhou Liao