A ferroelectric crystal is a material in which electric dipoles are arranged spontaneously below the Curie temperature to form electric domains, and can reverse spontaneous polarization with an applied electric field. A polar axis and an asymmetric center are necessary for ferroelectrics. Therefore, ferroelectrics below the Curie temperature must also have piezoelectricity. Ferroelectric materials exhibit a high dielectric constant for electrical signals and a large pyroelectric response to temperature changes. They have a strong piezoelectric effect and acousto-optic effect under the action of stress or sound waves, and have a significant effect under strong electric fields. Electro-optic effect. In addition, the ferroelectric material is excited by strong light, and the electrons are excited to cause spontaneous polarization changes, so that many new phenomena, such as the photorefractive effect, appear. Ferroelectric materials have excellent ferroelectric, dielectric, pyroelectric and piezoelectric characteristics, and have very important applications in solid-state devices such as ferroelectric memories, infrared detectors, surface acoustic waves, and integrated optoelectronic devices.
With the support of the 973 and 863 programs of the Ministry of Science and Technology, the National Natural Science Foundation of China, and the "Hundred Talents Program" of the Chinese Academy of Sciences, Luo Junhua's research team at the Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences, Fujian Institute of Material Structures proposed the The molecular motor is assembled into a novel molecular-based ferroelectric crystal material biimidazole tartrate. Its saturation polarization intensity Ps = 1.72 μC / cm2, and the corresponding coercive electric field value Ec ≈ 1.1 kV / cm. The researchers confirmed the phase transition from paraelectric phase to ferroelectric phase through the methods of single crystal diffraction, differential thermal analysis, variable temperature dielectric and variable temperature hysteresis loop.
Related research results were published in "German Applied Chemistry" (Angew. Chem., Int. Ed., 2012, DOI: 10.1002 / anie.201200407). The discovery of the ferroelectric crystal will provide new ideas for the synthesis and design of new molecular-based ferroelectric crystal materials.
The research team has also made a series of progress in the research of molecular-based photoelectric crystal materials (Inorg. Chem., 2012, DOI: 10.1021 / ic202406f; Cryst. Growth Des., 2011, 11, 2386-2397, 3744-3747; New J. Chem., 2011, 35, 2804–2810).
(a) Molecular-based ferroelectric phase transition from paraelectric phase to ferroelectric phase
(b) Molecular-based ferroelectric crystal
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