Hydroxyl group substitution extends working temperature for ferroelectric materials
Hydroxyl group substitution extends working temperature for ferroelectric materials lead image
Molecular ferroelectrics could be the materials of next-generation flexible electronic devices – particularly miniature ferroelectric devices – since they are easy to process into films, have good mechanical flexibility and are easy to tune. But one of the difficulties limiting their applications is their low transition temperature.
However, Ye et al. found an easy way to raise the transition temperature of ferroelectrics. The work builds on the group’s previous work studying molecular ferroelectrics and uses a hydroxyl substitution strategy, distinguishing from a previous F-substitution strategy, which replaces a hydrogen atom with a fluorine atom.
“We have demonstrated a simpler and more practical way to raise the transition temperature for molecular ferroelectrics, extending the ferroelectric working temperature from a low temperature to a moderate temperature,” said author Wei-Xiong Zhang.
In the study, the group introduced a hydroxyl group into a pyrrolidinium cation in order to raise the energy barriers through phase transition. The resulting enantiomeric hexagonal perovskite ferroelectrics were tested with a variety of methods including thermogravimetric analysis, differential scanning calorimetry and variable-temperature X-ray structural analysis.
The results showed the compound was thermally stable to high temperature and had a transition temperature of 350 K – much higher than the transition temperature of either parent material. Since fluoride substitution is difficult with organic molecules, the hydroxyl substitution offers a more practical way to raise the transition temperature in molecular ferroelectrics.
The researchers plan to continue the line of research by studying the effects with multi-component dense crystals on hydroxyl and amide groups.
“We anticipate that there will be a large room for hydroxyl substitution to enrich the molecular ferroelectric family,” Zhang said.
Source: “Two enantiomeric perovskite ferroelectrics with a high Tc raised by inserting intermolecular hydrogen bonds,” by Hui Ye, Wang-Hua Hu, Wei-Jian Xu, Ying Zeng, Xiao-Xian Chen, Rui-Kang Huang, Wei-Xiong Zhang, and Xiao-Ming Chen, APL Materials (2020). The article can be accessed at https://doi.org/10.1063/5.0035793 .
