钛酸铋钠（BNT）基陶瓷在大功率器件方面具有独特优势，但由于退极化温度低、电致应变的驱动电场与滞回性大，制约了其在压电滤波器、驱动器等方面的应用。本项目提出了采用第二相复合及淬火处理等方法，在BNT基陶瓷中构建局域应力场，通过局域应力场调控相变、结构并影响电畴转向，从而增强其压电性能的思路。通过改变第二相的热膨胀系数、颗粒大小与形貌、复合构型及淬火温度与淬火介质，实现对局域应力场的大小、分布及方向的有效控制；通过局域应力场抑制铁电-弛豫相变，增加极化后铁电相的稳定性，提高退极化温度；通过局域应力场诱导微观尺度的结构相变，降低电致应变的驱动电场；利用局域应力场对电畴的夹持作用，增加电畴翻转的阻力，降低电致应变的滞回性；最终揭示局域应力场对BNT基陶瓷压电性能的增强机理。所得研究结果不仅可以为压电陶瓷的改性提供理论指导，而且将丰富和发展压电陶瓷的多场耦合理论，为无铅压电陶瓷的实用化作出贡献。

Sodium bismuth titanate (BNT)-based ceramics have obvious advantages over other piezoelectric ceramics in terms of high-power applications, but the lower depolarization temperature, higher driving electric field and hysteresis of electrocstrain limit their applications in electronic components such as filters and actuators. This project intends to construct a local-stress field in BNT-based ceramics by employing the methods of compositing the second phase and quenching treatment, and achieve the enhancement of piezoelectric properties of BNT-based ceramics by tailoring the phase transition, microstructure and affecting the domain switching through the local-stress field. The detail are as following: the magnitude, distribution and direction of the local-stress field are regulated and effectively controlled by changing the thermal expansion coefficient, particle size and morphology of the second phase in the composite ceramics, composite configuration, quenching temperature and quenching medium; the ferroelectric-relaxor phase transition is restrained and the ferroelectric phase after poling is stabilized by the local-stress field, and thus the depolarization temperature of BNT-based ceramics is improved; the local-stress field induces microscopic structural phase transition, which increases the driving force of electro-induced phase transition, and thus the driving field of electrocstrain is reduced; the local stress field has a clamping effect on the domains, which increases the resistance of the domain switching, and thus the hysteresis of the electrocstrain is reduced; finally the effect of local-stress field on the enhancement of piezoelectric properties is clarified. The obtained results of this project not only provides theoretical guidance for the modification piezoelectric ceramics, but also enriches and develops the multi-field coupling theory of piezoelectric ceramics, contributing to the practical application of lead-free piezoelectric ceramics.