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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Above-room-temperature ferroelectricity in a single-component molecular crystal
Sachio Horiuchi1, Yusuke Tokunaga, Gianluca Giovannetti
1National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan. s-horiuchi@aist.go.jp
Nature
|February 12, 2010
Summary
Researchers achieved ferroelectricity in crystalline croconic acid by aligning molecular polarities with an electric field. This organic material exhibits high spontaneous polarization, paving the way for novel electronic applications.
Area of Science:
- Materials Science
- Organic Electronics
- Crystallography
Background:
- Ferroelectric materials exhibit unique electro-active properties like switchable polarity, pyroelectricity, and piezoelectricity.
- Organic ferroelectrics are desirable for flexible electronics, but achieving high spontaneous polarization remains a challenge.
- Croconic acid, a pentagonal molecule, possesses a hydrogen-bonded polar structure in its crystalline state.
Purpose of the Study:
- To demonstrate ferroelectricity in crystalline croconic acid through electric field-induced molecular alignment.
- To investigate the mechanism of polarization switching via topological pi-bond switching.
- To characterize the spontaneous polarization and thermal stability of this organic ferroelectric.
Main Methods:
- Applying an electric field to induce coherent alignment of molecular polarities in croconic acid crystals.
- Measuring optical second harmonic generation to confirm polarization alignment.
- Observing polarization hysteresis loops at room temperature.
- Performing first-principles electronic-structure calculations.
Main Results:
- Electric field application coherently aligned molecular polarities in croconic acid, evidenced by increased optical second harmonic generation.
- A well-defined polarization hysteresis loop was observed at room temperature, confirming ferroelectricity.
- The molecular crystal exhibited the highest spontaneous polarization (approximately 20 μC cm⁻²) among organic ferroelectrics, attributed to synchronized proton transfer.
- High polarization was maintained up to 400 K.
Conclusions:
- Crystalline croconic acid can be made ferroelectric through electric field-induced synchronized proton transfer, switching pi-bond topology.
- This organic ferroelectric material demonstrates exceptionally high spontaneous polarization for its molecular size.
- The robust ferroelectric properties up to 400 K suggest potential applications in active capacitors and nonlinear optics for organic electronics.
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