(K,Na)NbO₃ (KNN)-based piezoelectric materials are candidates for replacing Pb-based materials. However, the piezoelectric properties of existing KNN-based single crystals are still inferior to those of Pb-based relaxor ferroelectric single crystals. Moreover, the piezoelectric response mechanism of KNN-based single crystals remains unclear. In this study, (Li,K,Na)(Nb,Sb,Ta)O₃:Mn (KNNLST:Mn) single crystals with an excellent piezoelectric coefficient d₃₃ of approximately 778 pC/N were prepared. Systematically studies of intrinsic and extrinsic piezoelectric responses have revealed that the high d₃₃ of KNNLST:Mn single crystals is related to the shear piezoelectric response of a single-domain state and irreversible domain wall motion of the engineering domains. Furthermore, the effect of the orthorhombic (O)-tetragonal (T) phase boundary on intrinsic and extrinsic piezoelectric response is systematically studied, and the impact mechanism is elucidated. The results indicate that a lower dielectric response and elastic constant limit the intrinsic shear piezoelectric response of KNNLST:Mn single crystals, and approaching the O–T phase boundary can enhance both intrinsic and extrinsic piezoelectric responses. This study improves our understanding of the structure-performance relationship in KNN-based single crystals and offers insights for optimizing piezoelectric properties in KNN-based materials.

中文翻译：

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探索 （K，Na）NbO3 单晶中压电性能增强的机制


（K，Na）基于 NbO₃ （KNN） 的压电材料是替代 Pb 基材料的候选材料。然而，现有 KNN 基单晶的压电性能仍然不如 Pb 基弛豫铁电单晶。此外，基于 KNN 的单晶的压电响应机制仍不清楚。在这项研究中，制备了具有约 778 pC/N 的优异压电系数 d₃₃ 的 （Li，K，Na）（Nb，Sb，Ta）O₃：Mn （KNNLST：Mn） 单晶。对本征和外禀压电响应的系统研究表明，KNNLST：Mn 单晶的高 d₃₃ 与单畴态的剪切压电响应和工程畴的不可逆畴壁运动有关。此外，系统研究了正交 （O）-四方 （T） 相边界对本征和外征压电响应的影响，并阐明了影响机制。结果表明，较低的介电响应和弹性常数限制了 KNNLST：Mn 单晶的本征剪切压电响应，接近 O-T 相边界可以增强本征和外征压电响应。这项研究提高了我们对基于 KNN 的单晶结构-性能关系的理解，并为优化基于 KNN 的材料中的压电性能提供了见解。