无铅压电陶瓷中大于1%的超高电致应变：一项批判性综述
Ultrahigh electrostrain > 1% in lead-free piezoceramics: A critical review
AI总结：
本文通过复现NBT和KNN基无铅压电陶瓷的薄片实验，证明超高电致应变主要源于样品厚度减小而非缺陷偶极子，并质疑既有理论。
摘要：
近来，若干无铅压电陶瓷体系中出现了一系列显示超高电致应变（>1%）的报道。这种超高电致应变一直被完全归因于这些体系中产生的缺陷偶极子。我们基于另一项报告 arXiv:2208.07134 检验了这些主张；该报告证明，仅仅通过减小陶瓷圆片的厚度，所测得的电场驱动应变就会显著增加。我们制备了一些据报道可表现出超高应变的代表性无铅组分，并进行了电致应变测量。我们发现，当圆片厚度大于0.3 mm时（圆片直径在10–12 mm范围内），这些组分并不表现出超高电致应变。超高应变值是在厚度低于0.3 mm时获得的。我们在 Na0.5Bi0.5TiO3（NBT）和 K0.5Na0.5NbO3（KNN）基无铅体系中，将设计为具有缺陷偶极子的样品与未设计为具有缺陷偶极子的样品所得电致应变进行了比较，并且在小厚度范围内，可在无缺陷偶极子的压电陶瓷中获得高得多的应变水平（4–5%）。我们的结果并不支持将缺陷偶极子理论作为导致压电陶瓷超高应变的唯一因素。需要一种新的研究思路来理解由压电陶瓷圆片厚度减小所引起的超高电致应变现象。
英文摘要：
Recently, a series of reports showing ultra-high electrostrain (> 1 %) have appeared in several Pb-free piezoceramics. The ultrahigh electrostrain has been attributed exclusively to the defect dipoles created in these systems. We examine these claims based on another report arXiv:2208.07134 which demonstrated that the measured electric field driven strain increased dramatically simply by reducing the thickness of the ceramic discs. We prepared some representative Pb-free compositions reported to exhibit ultrahigh strain and performed electrostrain measurements. We found that these compositions do not show ultrahigh electrostrain if the thickness of the discs is above 0.3 mm (the disc diameters were in the range 10- 12 mm diameter). The ultrahigh strain values were obtained when the thickness was below 0.3 mm. We compare the electrostrain obtained from specimens designed to exhibit defect dipoles with specimens that were not designed to have defect dipoles in Na0.5Bi0.5TiO3 (NBT) and K0.5Na0.5NbO3 (KNN) -based lead-free systems and could obtain much higher strain levels (4- 5 %) in the defect dipole free piezoceramics in the small thickness regime. Our results do not favor the defect dipole theory as the exclusive factor for causing ultrahigh strain in piezoceramics. A new approach is called for to understand the phenomenon of ultrahigh electrostrain caused by the thickness reduction of piezoceramic discs.
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