Simulations uncover highly transparent ferroelectric piezoelectric crystal
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Simulations uncover highly transparent ferroelectric piezoelectric crystal
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uided by simulations, researchers from The Pennsylvania State University and Xi’an Jiaotong University have found a method for simultaneously increasing the transparency and piezoelectricity of rhombohedral lead magnesium niobite-lead titanate (PMN-28PT) crystals. The research team’s study was published recently in Nature (doi:10.1038/s41586-019-1891-y) and could be used to create better responsive, transparent touch screens. In many materials, it is a challenge to achieve transparency without sacrificing piezoelectric performance. Piezoelectric materials respond mechanically to an electric force and produce an electric signal under a mechanical force. The most important class of piezoelectric materials are ferroelectric materials that contain domains of permanent electric polarization. Without special treatment, these ferroelectric domains are randomly oriented along different crystallographic directions. To create piezoelectric devices, ferroelectric materials are poled, or exposed to an electric field, to align the different polarizations. Materials with high piezoelectricity have used poling to create engineered domain structures containing several types of ferroelectric domains separated by domain walls. “These domain walls severely scatter light, and hence these engineered domain structures are generally opaque,” says LongQing Chen of The Pennsylvania State University and a corresponding author of the recent Nature publication. The new results using PMN-28PT demonstrate that piezoelectric crystals containing domain walls can also be made transparent. Using a software package developed by Chen’s group, the research team simulated the behavior of the PMN28PT under both AC- and DC-electric fields, or AC- and DC-poling, respectively. While DC-poling has been widely used, their simulations showed that ACpoling gradually reduced the number of light-scattering domain walls in the PMN28PT crystal. Under the AC electric field, the different ferroelectric domains merge
(a) Photograph of two AC- (left, clear) and two DC- (right, yellow) poled rhombohedral Pb(Mg1/3Nb2/3) O3·PbTiO3 (PMN-PT) crystals. The thicknesses of the two crystals are 0.5 mm and 1.8 mm, respectively. (b) Light transmittance of the AC(red line and dots) and DC- (blue line and dots) poled PMN-PT crystals. (c) Piezoelectric coefficient and birefringence of the AC- and DC-poled PMN-28PT crystals. The red graded arrow shows the increase in the two properties for PMN-PT crystals after AC poling. Credit: Nature.
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as they “swing” back and forth, which led to a drastic reduction in the number of domains over time. Subsequent theoretical calculations confirmed that larger domain sizes lead to larger piezoelectric responses in the PMN-28PT crystals. Led by Zhuo Xu and Fei Li, the researchers at Xi’an Jiaotong University then used the simulation results to guide their processing of the PMN-28PT crystals to achieve high transparency. Building on a technique established 20 years
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