The schematic of the domain structures of barium titanate single crystals are calculated using phase-field simulations. Chane Research Group is located at Penn State.
The smaller the domain size in a ferroelectric crystal, the greater the piezoelectric properties of the material. Penn State researchers have raised questions about the standard rule.
ferroelectric materials can be flipped by applying an electric field. There are areas in the ferroelectric crystal that have the same dipole moments. Piezoelectricity is a material property where the crystal has an electrical charge. Piezos can be used in electronics.
Bo Wang, a scholar in materials science and engineering, said that many devices in our daily life use the ability of a material to convert electrical signals to mechanical signals. The piezoelectric material is a key part of most of these applications. ferroelectric materials are the most advanced.
ferroelectric materials have many domains and range in size from a few nanometers to as much as millimeters. When there is a separation of charge, each domain has a uniform distribution of dipole moments. The domain walls are regions between adjacent domains.
The domain walls in ferroelectric crystals are interfaced with a very small thickness over which the dipole moments change their directions. It's well known in the research community of ferroelectric materials that domain walls have a strong influence on piezoelectricity. There is a belief in the community that the larger the domain wall density, the larger the piezoelectric coefficient.
Wang and his co-workers published work in Advanced Materials that challenges this conventional wisdom.
Wang said that the computation view is not often correct.
The idea that smaller domains lead to higher piezoelectricity is based on limited data.
One of the first things that comes to mind when you think of the research community is the fact that they have tried to make all these domains smaller to enhance the piezoelectricity, and often when they see some improvement in the performance, one of the first things that comes to mind is the smaller The work provides a theoretical foundation for the correlation of the piezoelectricity to crystal symmetry, crystal orientation, and domain configuration.
The paper referred to findings that an AC electric field can improve the crystal's piezoelectric response by 20% to 40% compared with a DC electric field. The team discovered that the domain sizes inside the crystal were larger than they would have been expected to be.
"We proposed a theoretical model of domain change under electric fields, we use computation to confirm it, and because of our simulation, we have shown that researchers in the future will have to look inside the crystal," Chen said. The previous researchers only looked at the surface, but they showed that the larger the domain, the higher the response. We showed that the domain became bigger with higher piezoelectricity, and that was found by examining under the crystal's surface.
Wang says that the new understanding of the relationship between ferroelectric crystal domain size and piezoelectricity can help improve the performance of materials.
"We hope that this study will allow people to rethink the design principles for piezoelectric materials, perhaps creating better piezoelectric materials in ways that were not thought possible before," Wang said. "This may enable better piezoelectrics made from lower-cost materials, or from materials that are more eco-friendly."
The other author on the study was a previous researcher at Penn State who is now a full professor at a Chinese university.
Bo Wang and his colleagues wrote about size dependence of piezoelectricity in ferroelectric crystals. A document titled "10.1002/adma.202105071".
Journal information about advanced materials.
The study challenges standard ideas about piezoelectricity in ferroelectriccrystals.
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