CeO2基-非化学计量LaGaO3基复合电解质的界面调控及导电性能

Interfacial structure has an significant influence on oxygen-ion transport and storage. To manipulate the compositions, structures and chemical defects of grain boundary/interface by using grain-boundary effect of the polycrystalline materials and interfacial effect of the composite materials, and explore its structure-activity relationships are important subjects in material area. In this project, we perform the first principles calculations of the effects of A- and B-site non-stoichiometry on crystal structures, bands and oxygen defects in LaGaO3(ABO3) perovskite materials. The LaGaO3 based materials with different particle sizes, contents and non-stoichiometries are introduced into CeO2 based electrolytes by several approaches, and its effects on grain boundary phases, space charge layers, sintering densification and electrical properties of the high-pure/impure CeO2 based electrolytes are investigated. Our efforts are manipulate the interfacial structure of composite electrolyte from three aspects that including the nonstoichiometry modulation to microstructure in LaGaO3, the structure differences between the CeO2 and LaGaO3 phases, and the concept of nanocomposite electrolyte. We clarify the driving factors of the ionic single/double diffusion by hetero-interfaces, and the impurity ionic distribution among the the grain boundary or grain interior. We attempt to manipulate the formation and evolution processes of the compounds and defects in interfaces. The optimum experimental condition and sintering process are explored to prepare the nano dense composite ceramics. Our ultimate aim is to effectively reduce the grain boundary/interface resistances, and obtain high performance composite oxide electrolyte materials.

界面结构影响氧离子的输运与存储。利用多晶材料的晶界特性和复合材料的界面效应，控制晶界/界面的组成、结构和缺陷，探索其构效关系是材料科学研究的重要课题。本项目针对钙钛矿LaGaO3材料中A位和B位的非化学计量对晶体结构、能带及缺陷的影响，利用第一性原理进行计算。采用多种方法将不同颗粒尺寸、不同质量比及不同非化学计量LaGaO3基材料引入CeO2基电解质，考察其对高纯/非纯CeO2基电解质的晶界相、空间电荷层效应、烧结致密化和电性能的影响。利用LaGaO3基非化学计量对微结构的调变、CeO2和LaGaO3两相结构的差异及纳米复合的理念调控复合电解质的界面结构；明确异质界面离子单/双向扩散的驱动因素及杂质离子在晶界或晶粒内分布；控制界面化合物及缺陷的形成与演变规律。探索改进和优化实验条件及材料的烧结工艺，制备纳米化致密复合陶瓷。旨在降低材料的晶界/界面电阻，获得高性能的复合氧化物电解质材料。

界面结构影响氧离子的输运与存储。利用多晶材料的晶界特性和复合材料的界面效应，控制晶界/界面的组成、结构和缺陷，探索其构效关系是材料科学研究的重要课题。本项目针对钙钛矿LaGaO3材料中A位和B位的非化学计量对晶体结构、能带及缺陷的影响，采用溶胶凝胶方法制备 (La0.9Sr0.1)x(Ga0.9Mg0.1)yO3-δ（(LS)x(GM)y，x = 0.97,1.00,1.03，y=1.00和x = 1.00，y=0.97,1.00,1.03）电解质。通过调变Ａ位或Ｂ位的非化学计量，改善样品的相纯度，减少杂质相含量，影响电解质的导电性能和热膨胀性能。B位缺陷的LS(GM)0.97样品呈现最高的相纯度、致密性，最小的晶界体积分数、晶界电阻和总电阻，以电解质支撑的NiO-GDC|GDC|LS(GM)0.97|LSCF单电池在800℃下的最大功率密度达到0.54W•cm-1，比LSGM基单电池提高约16.7％。从多种氧化物中（MoO3、FeO1.5、CoO、ZnO、WO3和Bi2O3）筛选出适宜NDC体系、LSGM体系及其复合体系的烧结助剂和最适加入量；并探讨其致密化机理。研究SrO/MgO掺杂的LaGaO3钙钛矿（LSGM/LSG/LGM）添加于高纯和非纯NDC体系，对晶界处富集SiO2的清除作用，同时，研究LSGM/LSG/LGM与NDC间的相界面复合作用，A位掺杂SrO的LSG晶界电导性和总电导性均比B位掺杂MgO的LGM好，LSGM集LSG和LGM的共同优点，晶界电导率和总电导率最佳。建立不同体系的晶界/界面导电模型。探讨了多功能氧化物钨酸铋对NDC体系的烧结行为、相组成、微观结构、电性能和热稳定性的影响；总结了制备纳米化致密复合陶瓷的最佳制备方法和烧结工艺条件；获得高性能中低温SOFCs复合电解质材料。