AgNbO3基无铅反铁电陶瓷的组分调控与电学性能研究

The high polarization and double hysteresis loop of AgNbO3 under high electric field provide an opportunity on the solution of improving the energy density of capacitors and the released charge of explosive to electrical materials. AgNbO3 is chosen to be the base composition. Based on the crystal structure of perovskite compounds, the tolerance factor t and electronegativity difference X, the two main factors affecting the stability of perovskite structure, will be introduced, and the structural modification of AgNbO3 will be carried out through different A-site and B-site cation substitutions. AgNbO3-based lead-free antiferroelectric ceramics will be prepared via a solid state reaction approach in flowing O2. By reducing the tolerance factor t and increasing the electronegativity difference X, the antiferroelectric phase will be stable to obtain lead-free energy storage materials with high energy storage density, high energy conversion efficiency and good anti-fatigue features. By increasing the tolerance factor t and the electronegativity difference X, the ferroelectric phase will be stable to obtain lead-free explosive to electrical materials with high released charge, low phase transition pressure and good thermal stability. Meanwhile, the effect of different A-site and B-site cation substitutions on the crystal structures and electrical properties will also be systematically discussed from the point of oxygen octrahedral distortion and tolerance factor t. The cation selection criteria and doping principles for the preparation of high quality AgNbO3-based lead free antiferroelectric materials will also be presented. These studies will provide theoretical and experimental basis for the design of other lead-free antiferroelectric materials.

AgNbO3电场作用下极高的极化强度和双电滞回线的特质，为提高储能电容器的储能密度和爆电换能材料的释放电荷等难题的解决带来了契机。本项目以AgNbO3为研究对象，根据钙钛矿化合物的晶体结构特征，综合考虑影响钙钛矿结构稳定性的两个主要因素（容忍因子t和电负性差X），通过A/B位不同阳离子的组合对其进行结构协调改性，氧氛围下制备系列AgNbO3基无铅反铁电陶瓷。通过减小容忍因子t和增加电负性差X，稳定反铁电相，获得储能密度和能量转换效率高、抗疲劳特性好的无铅反铁电储能材料；通过增大容忍因子t和增加电负性差X，稳定铁电相，获得释放电荷量高、相变压强低、热稳定好的无铅爆电换能材料。同时，研究A/B位不同阳离子掺杂对AgNbO3基无铅反铁电陶瓷晶体结构和电学性能的影响，定性地给出制备高质量AgNbO3基无铅反铁电陶瓷的离子选择准则以及掺杂原则，为其他无铅反铁电材料的组分设计提供理论依据和实验基础。

AgNbO3基无铅反铁电储能陶瓷因其电场下极高的极化强度和反铁电双电滞回线的特质，成为一种有望替代含铅储能陶瓷的候选材料，其强场下的电学性能及应用开始成为研究热点。银含量较高的化合物在空气氛围下烧结易分解成氧化银，使材料的相结构不纯，造成材料的漏导比较大，因此，纯相的AgNbO3基无铅反铁电陶瓷在空气氛围下难以制备。本项目以AgNbO3为基础设计模型，在维持电价平衡的前提下，基于容忍因子和平均极化率，采用A/B位金属阳离子共掺的方法，通过控制氧气流速、炉腔内氧气压强、升降温速率以及保温时间等因素，在氧氛围下成功制备出系列高质量的AgNbO3基无铅反铁电储能陶瓷；通过XRD、XPS、SEM等测试手段，对AgNbO3基陶瓷的微观结构进行了系统研究，揭示了不同A/B位阳离子取代对相结构及固溶限制的影响和机制；系统研究了组分变化对M1→M2、M2→M3等相变温度和电场诱导相变的影响，揭示了晶体结构与电学性能的关联性；研究了不同组分的储能密度、储能效率、弛豫行为和温度稳定性，确定了具有较高储能密度和储能效率、温度稳定性好的材料组分。通过本项目的研究，从氧八面体结构畸变和容忍因子t变化的角度出发，研究了A/B位不同阳离子掺杂对AgNbO3基无铅反铁电陶瓷晶体结构和电学性能的影响及其机制，定性地给出了制备高质量AgNbO3基无铅反铁电材料的离子选择准则以及掺杂原则，为其他AgNbO3基无铅反铁电材料的组分设计提供了理论依据和实验基础。