Large Piezoelectric Response in a Metal-Free Three-Dimensional Perovskite Ferroelectric
Hua Zhang, Zhe‐Kun Xu, Zhong‐Xia Wang, Hang Z. Yu, Hui‐Peng Lv, Peng‐Fei Li, Wei‐Qiang Liao, Ren‐Gen Xiong
Abstract
Metal-free perovskites with light weight and eco-friendly processability have received great interest in recent years due to their superior physical features in ferroelectrics, X-ray detection, and optoelectronics. The famous metal-free perovskite ferroelectric MDABCO-NH 4 -I 3 (MDABCO = N -methyl- N ′-diazabicyclo[2.2.2]octonium) has been demonstrated to exhibit excellent ferroelectricity comparable to that of inorganic ceramic ferroelectric BaTiO 3, such as large spontaneous polarization and high Curie temperature (Ye et al. Science 2018, 361, 151). However, piezoelectricity as a vitally important index is far from enough in the metal-free perovskite family. Here, we report the discovery of large piezoelectric response in a new metal-free three-dimensional perovskite ferroelectric NDABCO-NH 4 -Br 3 (NDABCO = N -amino- N ′-diazabicyclo[2.2.2]octonium) by replacing the methyl group of MDABCO with the amino group. Besides the evident ferroelectricity, strikingly, NDABCO-NH 4 -Br 3 shows a large d 33 of 63 pC/N more than 4 times that of MDABCO-NH 4 -I 3 (14 pC/N). The d 33 value is also strongly supported by the computational study. To the best of our knowledge, such a large d 33 value ranks the highest among the documented organic ferroelectric crystals to date and represents a major breakthrough in metal-free perovskite ferroelectrics. Combined with decent mechanical properties, NDABCO-NH 4 -Br 3 is expected to be a competitive candidate for medical, biomechanical, wearable, and body-compatible ferroelectric devices.