Metal-free three-dimensional perovskite ferroelectrics

• Published in: Science (American Association for the Advancement of Science) Vol. 361; no. 6398; pp. 151 - 155
• Main Authors: Ye, Heng-Yun, Tang, Yuan-Yuan, Li, Peng-Fei, Liao, Wei-Qiang, Gao, Ji-Xing, Hua, Xiu-Ni, Cai, Hu, Shi, Ping-Ping, You, Yu-Meng, Xiong, Ren-Gen
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 13.07.2018
• Subjects: Ammonium; Barium; Barium titanates; Biomedical materials; Ferroelectric materials; Ferroelectricity; Ferroelectrics; Organic Chemistry; Organic compounds; Perovskite structure; Perovskites; Phase transitions; Polarization; Synthesis; Transition temperature; Transition temperatures
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.aas9330

The perovskite structure accommodates many different combinations of elements, making it attractive for use in a wide variety of applications. Building perovskites out of only organic compounds is appealing because these materials tend to be flexible, fracture-resistant, and potentially easier to synthesize than their inorganic counterparts. Ye et al. describe a previously unknown family of all-organic perovskites, of which they synthesized 23 different family members (see the Perspective by Li and Ji). The compounds are attractive as ferroelectrics, including one compound with properties close to the well-known inorganic ferroelectric BaTiO 3 . Science , this issue p. 151 ; see also p. 132 A family of all-organic perovskites has attractive ferroelectric properties. Inorganic perovskite ferroelectrics are widely used in nonvolatile memory elements, capacitors, and sensors because of their excellent ferroelectric and other properties. Organic ferroelectrics are desirable for their mechanical flexibility, low weight, environmentally friendly processing, and low processing temperatures. Although almost a century has passed since the first ferroelectric, Rochelle salt, was discovered, examples of highly desirable organic perovskite ferroelectrics are lacking. We found a family of metal-free organic perovskite ferroelectrics with the characteristic three-dimensional structure, among which MDABCO ( N -methyl- N' -diazabicyclo[2.2.2]octonium)–ammonium triiodide has a spontaneous polarization of 22 microcoulombs per square centimeter [close to that of barium titanate (BTO)], a high phase transition temperature of 448 kelvins (above that of BTO), and eight possible polarization directions. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications.