电场诱导钙钛矿中有序畴结构与Q值优化研究

In A(B'1/3B''2/3)O3 and A(B'1/2B''1/2)O3 type complex perovskites, the B-site long range ordering (LRO) structure is significantly important to these ultra high Q value materials. In order to obtain the LRO structure, long time annealing process is generally necessary, which is unbenefit for the improvement of producing efficiency and will cause secondary abnormal grain growth or secondary phases due to element evaporation, which will in turn deteriorate the Q value. Aiming at this problem, in the present project, an AC electric field is applied during the annealing process to assist the driving force of the B-site LRO domain structure in these complex perovskites. And through tuning the frequency and voltage of the AC electric field, we try to control and improve the B-site LRO structure. By employing the AC electric field, the annealing time and temperature will be substantially decreased, while the B-site LRO structure will still be improved. The microstructure evolution kinetics under the applied AC electric field will be revealed. Finally, through electric field assisted annealing process, the Q value in the above two types of complex perovskites will be significantly improved compared with the corresponding samples produced by the traditional annealing process. And by comparing the dielectric behavior of the LRO samples with the corresponding disordered samples under GHz wave and THz wave frequency, the physical relationship between LRO structure and Q value will be revealed detailly.

在A(B'1/3B''2/3)O3及A(B'1/2B''1/2)O3型复合钙钛矿材料中，其B位阳离子的长程有序结构对Q值的影响至关重要。为了获得长程有序畴结构，往往需要对材料进行长时间的退火处理，这即不利于生产效率的提高，又容易引起二次晶粒长大及元素挥发而造成第二相等问题，反而会恶化Q值。 本项目针对这一问题，通过在退火过程中引入交流电场来辅助驱动上述复合钙钛矿中的B位阳离子的长程有序畴结构，并通过施加电场的电压和频率等参数加以调控。使得在退火时间及退火温度大幅减小的同时，B位阳离子有序度依然得以优化，并揭示电场温场耦合驱动下复合钙钛矿中微观结构演变的动力学特征。本项目最终将实现在上述两种类型的钙钛矿中电场辅助退火的样品比相应传统退火的样品的Q值有显著提升，并通过对比具有有序、无序结构的样品在GHz波段与THz波段的介电行为，揭示有序畴结构与Q值之间的深层物理关系。

复合钙钛矿结构的陶瓷在微波波段的介电损耗特性强烈依赖于其结构中B位阳离子的有序结构，当B位的两种阳离子有序度教高时钙钛矿对电磁波的损耗最小。.为了获得这样的有序结构，本项目通过在陶瓷烧结工艺中引入电场退火，在AB1/3B2/3O3及AB1/2B1/2O3等结构的陶瓷中，能实现缩短陶瓷的退火时间、降低退火温度的同时使陶瓷的介电损耗还优于传统工艺制备的同类陶瓷。项目揭示了电场退火下的烧结动力学机制，表明有序/无序相变在电场的辅助驱动下将更快的、在更低的温度下发生，而且电场还能加速氧空位等点缺陷沿晶界的迁移，使晶界变得更“干净”。.介电损耗的优化物理根源在于无序结构中空间电荷产生的内建电场的产生会使复合钙钛矿陶瓷的振子阻尼系数Γi增大。项目还研究了上述复杂钙钛矿在MHz、THz波段介电性能的关系。通过不同波段下的介电性能揭示了其高Q值与本征因素（晶格有序度）及非本征因素（致密度、杂相、晶粒尺寸等）之间的物理关系：THz波段，本征因素（有序无序相变）是介电损耗的主要来源，而KHz、MHz等低频段，非本征因素（空位、缺陷、晶界杂质及晶粒大小等）则是介电损耗的决定因素。.项目提出的这一方法及其实现的机理将有利于钙钛矿介质陶瓷在5G移动通讯系统的滤波器、天线等领域的应用，能提高器件的选频性能，使其通话质量更好。