缺陷偶极子诱导BNT基陶瓷可逆应变及窄滞后机理研究

Poor strain and large hysteresis of piezoelectric ceramics restrict their application in actuators. This project targets on relaxor ferroelectricity BNT-based ceramic, and raise the design thought that utilizing both effects of the domains swiching caused by defect dipoles and the phase transition induced by electric field to achieve lead-free piezoelectric materials with large strain and dramatically improved hysteresis. Defect dipoles can be introduced into BNT-based ceramics with different phase structures by modifying with acceptor impurities, the strain and hysteresis of the ceramics with T phase structure can be improved through domains swiching caused by defect dipoles, and the strain properties of the ceramics with ferroelectric-relaxation coexistence phase structure can be further enhanced by the combined contribution of defect dipoles and electric field induced phase transition. The effects of both phase structure and donor doping on the forming condition and the distribution of the defect dipoles will be studied in detail. The mechanism of improving strain value and hysteresis caused by defect dipoles will be revealed. The relations between microstructure, dielectric, ferroelectric and strain properties will be established. The influence and mechanism of the combined effect of phase transition and defect dipoles on huge strain will be also investigated. The results given by this present study will be significant for the design of novel piezoelectric material with high strain and narrow hysteresis.

针对压电陶瓷在驱动器等领域的应用中存在应变小、滞后严重的瓶颈问题，本项目以弛豫铁电体BNT基陶瓷为研究对象，提出利用缺陷偶极子使畴翻转和电场诱发相变的共同作用获得应变大、滞后明显改善的无铅压电材料的设计思路。通过受主掺杂在不同相结构的BNT基陶瓷晶格内构建缺陷偶极子，利用缺陷偶极子使畴翻转改善T相区陶瓷应变大小及滞后性，利用缺陷偶极子及电场诱发相变的共同作用进一步优化铁电-弛豫共存相区BNT基陶瓷的应变性能。深入系统地研究BNT基陶瓷的相结构及施主掺杂对缺陷偶极子形成条件及分布的影响规律，揭示缺陷偶极子改善应变大小及滞后性的机理，建立陶瓷微观结构与介电、铁电及应变性能的内在联系，阐明电场引发相变及缺陷偶极子的共同作用对诱发陶瓷产生大应变效应的影响规律与机制。本研究为设计大应变、窄滞后的新型压电材料具有重要指导意义。

针对压电陶瓷在驱动器等领域的应用中存在应变小、滞后严重的瓶颈问题，本项目以弛豫铁电体BNT基陶瓷为研究对象，提出利用缺陷偶极子使畴翻转和电场诱发相变的共同作用获得应变大、滞后明显改善的无铅压电材料的设计思路。研究发现，B位受主掺杂Mn2+能在T相区和铁电与弛豫共存相区的BNT-ST陶瓷晶格内形成Mn2+-V•• O缺陷偶极子。T相区内的缺陷偶极子使畴翻转可逆改善了陶瓷应变大小及滞后性，在MnO掺杂量为0.5 mol %的0.7BNT-0.3ST陶瓷中获得S=0.32%，H=28%的应变性能；铁电与弛豫共存相区内缺陷偶极子在诱发畴翻转可逆，同时，缺陷偶极子形成的局域场和应力场增强了陶瓷的遍历性，提高电场诱导相变的可恢复性，在缺陷偶极子及电场诱发相变的共同作用下得到S=0.62%，H=10.9%的优异应变性能。B位施主Nb5+掺杂能够在T相区和铁电与弛豫共存相区的BNT-ST陶瓷晶格内形成Nb5+-Ti3+离子对偶极子，离子对偶极子形成的内建电场能降低两个相区内BNT-ST陶瓷的应变滞后性，提高铁电-弛豫共存相区陶瓷的应变大小。在0.5mol% Nb5+时掺杂0.75NBT-0.25ST陶瓷中获得S=0.36%，H=36%的应变性能。施主-受主共掺杂对BNT基陶瓷应变性能的影响较小。本研究结果为设计大应变、窄滞后的新型压电材料具有重要指导意义。