Ferroelectric materials commonly found in the fields of memory, piezoelectric components, etc. If they obtain the elasticity of rubber bands, it is expected to make the sensor shape changeable and the mobile phone more easily bent and folded.
On August 4, the international academic journal Science published the scientific research results of the flexible magnetoelectric functional materials and devices team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences—— was the first in the world to develop a new polymer ferroelectric material with elastic recovery and ferroelectricity, effectively solving the problem that traditional ferroelectric materials are difficult to maintain stable performance under large deformation and filling the gap in the field of elastic ferroelectric materials.
Ferroelectric materials are prone to failure when stretched
“Ferroelectric materials are a magical insulating functional material. The surface is charged and when there is no external electric field, these charges are in disorder. ”The corresponding author of the paper and researcher Hu Benlin from the Ningbo Institute of Materials, Chinese Academy of Sciences, introduced that once an electric field acts on the ferroelectric material, these charges will be rearranged, and the arrangement will change with the change of the electric field.
In addition, ferroelectric materials have memory capabilities. Even if the electric field no longer acts, the arranged charge will remain in its original state without changing. This makes ferroelectric materials have high dielectric constant, piezoelectricity, thermoelectricity, electrical refrigeration properties, etc., and can be used in electronic products such as computer memory, high-precision motors, ultra-sensitive sensors, sonar equipment, and one of the essential materials in electronic devices such as mobile phones and tablets.
In recent years, research on flexible wearable devices has remained popular, and these devices are believed to have broad application prospects in the fields of portable mobile electronic devices and human motion detection. As one of the important materials for manufacturing flexible wearable devices, if ferroelectric materials can be elasticized, they can contribute to the development of this industry.
“But it is difficult to study and prepare elastic ferroelectric materials. ”Hu Benlin explained that traditional ferroelectric materials are mainly linear structures, and the arranged parts form crystalline regions to provide ferroelectricity, while the remaining molecular chains are entangled with each other. Since there is no covalent connection between linear molecular chains, once an external force is applied, this mutual entanglement will be untangled, which will lead to the destruction of the crystallization region and affect its ferroelectricity.
Kao Liang, the first author of the paper, a joint training master student from the School of Nanotechnology of the University of Science and Technology of China and the Ningbo Institute of Materials, Chinese Academy of Sciences, added that the crystal itself is almost not elastic, the elongation rate is generally less than 5% and has no rebound ability, so it is difficult for ferroelectric materials to take into account both ferroelectricity and elasticity.
“Microcrosslinking method ”Weaving “Fishing net ”Get elasticity
Sugarcane cannot be sweet at both ends? In this study, through precise design and control of the material structure, researchers prepared an elastic material that still has good ferroelectric response under high frequency and large deformation. After stretching it to twice the original length, it not only maintains the original ferroelectricity, but also quickly restores to its original state after the external force is removed, achieving the balance between ferroelectricity and elasticity of ferroelectric materials.
The method of preparing elastic ferroelectric materials is called the “ micro-crosslinking method;”—— the team called the “ — using trace amounts of soft chain polymer, the amorphous wound parts around the ferroelectric crystal are crosslinked, interwoven with each other to form an elastic fishnet-like structure. Similar to placing the crystal and winding parts in a “ fishing net ” making a ferroelectric “ with good elastic recovery ability.
Hu Benlin introduced that the team tried dozens of materials before finding a suitable chain polymer. This fishing net-like structure loosely connects ferroelectric crystals together. When external forces act, reversible deformation can be generated to absorb external forces and avoid the damage of external forces to the crystallization part, so that the material can still maintain stable ferroelectricity within a certain stretching range; when external forces are cancelled, this elastic fishing net-like structure can return to the initial state.
“In addition, precise control of the amount of chain polymer can ensure that the ferroelectric crystal can be evenly distributed in the crosslinking network, so that the material can maintain a good ferroelectric response after crosslinking. ”Hu Benlin said that this elastic ferroelectric material can withstand thousands of repeated stretches while the ferroelectricity remains stable. It can restore its original state after being subjected to stress, avoid permanent deformation, greatly improves reliability and service life, and expands the scope of use.
The reviewer of the journal Science commented that in the century-old history of ferroelectric materials after their discovery, compared with the elastic recovery of ferroelectric ceramics of less than 0.2% to less than 2% of polymer ferroelectric materials, this is a breakthrough work, opening up a new "elastic ferroelectric" discipline direction.