Effect of stress on ferroelectric properties in flexible BiFe_0.97Cr_0.03O₃/BiFe_1−xMn_xO₃ composite thin films

Wearable devices and flexible electronics have promoted the development of flexible thin film materials. Flexible films with excellent performance and adapted to the operating conditions of flexible electronic devices are required. Here, the flexible BiFe_0.97Cr_0.03O₃/BiFe_1−xMn_xO₃ (x = 0.05–0.09) ferroelectric thin films were successfully prepared on LaNiO₃/fluorophlogopite (F-Mica) by the sol–gel method. The flexible BiFe_0.97Cr_0.03O₃/BiFe_0.93Mn_0.07O₃ (BFC_0.03O/BFM_0.07O) sample shows a best ferroelectricity with a real residual polarization value of 106.59 µC/cm² was obtained from the Positive Up Negative Down (PUND). The flexible sample maintains true ferroelectric performance at different frequencies and shows excellent bending fatigue resistance after mechanical bending with 10000 cycles. The residual stress generated by mechanical bending increases the polarization of the flexible sample while maintaining the true ferroelectric polarization. The larger residual stress results in the enlargement of the defect. This provides an interesting approach to the ferroelectric regulation of flexible thin films. The flexible BiFe_0.97Cr_0.03O₃/BiFe_1−xMn_xO₃ thin films with excellent ferroelectricity and bending fatigue resistance are promising for the applications in high temperature flexible electronic components and sensors.