Experimentally confirmed ferroelectricity in organic compounds identified by database mining

Abstract

Compared to inorganic ferroelectrics, the breadth of polarization switching mechanisms in organic ferroelectrics is very broad and far from fully characterized or understood. Here, we experimentally investigate the absence or presence of ferroelectric properties in a selection of organic materials that have been identified by a data mining approach using heuristic measures to identify stretchability, aiming to assess the practical potential of this approach. From a set of 66 candidate materials, 4 were selected for detailed analysis. These were investigated structurally using powder X-ray diffraction and electrically, using capacitance–voltage spectroscopy and polarization hysteresis measurements. Despite large differences in stability and background conductivity, all compounds exhibited ferroelectric behavior at room temperature, with relatively large polarization values. Specifically, the ferroelectric properties of one material show a strong dependency on the ambient humidity, whereas another showed a strong coupling between background conductivity and ferroelectric switching. These effects are not yet fully understood and lie beyond the scope of this study. Of the remaining two compounds, one was found to be unstable at room temperature whereas the other displayed multiple polymorphs, complicating reproducibility and limiting their practical potential. Overall, these results confirm the relevance of the data mining prediction scheme and suggest that a significant fraction of the identified but so far untested materials may also be ferroelectric.