Piezoelectric materials can change mechanical energy to electrical energy. There has been a growing interest in the search for two-dimensional piezoelectrics. It's useful for niche applications such as actuator with atomic-scale precision and Wearable sensors. 2D Piezos can be used as power generators for small devices.
On an ad hoc basis, the discovery of 2D piezoelectrics has been made. A systematic search through a 2D materials database is needed to find 2D materials which are most suited for use. A research team from the Department of Physics at the National University of Singapore conducted a systematic search through a database of 2,940 van der Waals materials using high-throughput first principles calculations. The team identified a number of materials that have piezoelectric effects. NbOI 2 is found to have the largest piezoelectric coefficients among the materials. Piezo performance can be improved by materials with high coefficients.
The predicted electromechanicalcoupling factor of NbOI 2 has the highest possible value of unity in this material. The research team isolated few-layer NbOI 2 crystals and used lasers to measure their piezoelectric response. They found that NbOI 2 displayed a larger response than reference materials.
NbOI 2 is part of a family of niobium oxydihalides which have large coefficients of piezoelectricity. The crystal structure of NbOX 2 is not symmetrical in the x-direction, which was discovered by the researchers in a more detailed study. The ferroelectric polarization is the largest for NbOCl 2.
The class of NbOX 2 materials has a lot of potential. The NbOI 2 had the best piezoelectric performance in our study. We discovered that its performance is not dependent on thickness. When there is an even number of layers, this is a different type of 2D piezoelectric. It's useful for practical applications where the control of the material thickness may be particularly challenging.
More information: Yaze Wu et al, Data-driven discovery of high performance layered van der Waals piezoelectric NbOI2, Nature Communications (2022). DOI: 10.1038/s41467-022-29495-y Journal information: Nature Communications
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