界面区异价元素掺杂对CeO2基电解质空间电势调控及导电行为的影响

Based on the fact that the electrical conductivity behavior of CeO2-based solid electrolyte is affected and controlled by the interfacial space potential directly, it is significant to improve the electrical properties of this electrolyte through the adjustment and control of the interfacial space potential by means of doping the aliovalent elements from both theoretical and practical aspects. In this project, aiming at the interfacial characteristics of the electrolytes with both equiaxed and columnar microstructures, the methods of "encapulsating the grain particles" and "grain boundary diffusion+heat treatment" are adopted respectively to dope the aliovalent metal ions into the interface in order to adjust the space potential and improve the electrical conductivity. The research contents include: ①equiaxed CeO2-based ceramics will be prepared through encapulsating the grain particles combined with different sintering processes so that the elements can be doped into the interface and their distribution and segregation can be controlled. ②CeO2-based films with the columnar structure will be fabricated by magnetron sputtering process, and a diffusion layer composing of aliovalent metal elements will be deposited on their surface continuously. The diffusion along the grain boundary and the doping of the elements will be realized by a consequent rapid annealing process. ③the mechanisms about the interactions between the doped ions and the matrix elements will be analyzed, and the regulations about the influences of the aliovalent doped ions on the interfacial space potential will be discovered. The optimal process about the adjustment and control of the interfacial space potential will be determined to improve the electrical conductivity of the CeO2-based ceramics. This project will contribute to the increment of the electrical conductivity of the CeO2-based solid electrolytes, the extension of their application fields and the establishment of the corresponding theoretical basis.

CeO2基固态电解质的导电行为直接受界面空间电势的影响和控制，通过在晶界区掺杂异价元素调控界面空间电势、改善其电导性能具有重要的理论和现实意义。本项目针对等轴晶和柱状晶结构CeO2基电解质的界面特征，拟分别采用"晶粒包覆烧结"和"晶界扩散+热处理"工艺实现异价元素的晶界掺杂和界面空间电势调控，进而灵活调控其导电行为。研究内容包括：①采用晶粒包覆法结合不同的烧结制度制备等轴晶CeO2基陶瓷，实现元素的掺杂并控制其在晶界区的分布、偏析。②采用磁控溅射法制备柱状晶结构CeO2基薄膜并在其表面连续沉积异价元素扩散层，利用快速退火工艺实现该元素沿晶界的扩散掺杂。③分析和建立异价掺杂离子与基体元素的作用机制，揭示不同价态离子对晶界空间电势调控的影响规律，确定通过空间电势调控改善CeO2基电解质导电行为的工艺途径。本项目将为改善CeO2基电解质的电导特性、拓展其应用范围探索新的途径并奠定相应的理论基础。

CeO2基固态电解质是一种重要的氧离子导体，被广泛用于固体氧化物燃料电池、氧传感器等领域，由于受界面空间电势和界面区杂质相的影响，其晶界电导率仍亟待提高。本项目首先通过共沉淀法和晶界包覆法制备出Fe、Co掺杂的GDC样品，研究了Fe和Co的晶界包覆掺杂对CeO2基固态电解质电导性能的影响，随着掺杂元素含量的增加，衍射峰向低角区偏移。陶瓷样品的晶粒尺寸为59.8～112nm。通过包覆掺杂方法得到的陶瓷样品电导率增加了近2倍。晶界区域Fe元素的添加，起到了清除晶粒之间硅质相的作用，从而提高样品的电导率。之后通过添加Al2O3异质相制备了SDC20-Al2O3纳米复相陶瓷，研究了Al2O3的掺杂比例、烧结温度、保温时间对复相陶瓷电导行为的影响规律。在烧结温度为1200℃时制备出的SDC20-Al2O3复相陶瓷中只存在SDC20相和Al2O3相，随Al2O3掺入量的增加，烧结样品的相对密度逐渐增加，复相陶瓷的电导率呈现先升高后降低的趋势。当Al2O3掺杂含量为30vol%时，SDC20-Al2O3复相陶瓷的离子电导率最大，不同配比的SDC20-Al2O3复相陶瓷的离子迁移数均大于0.94。最后项目组采用反应磁控溅射工艺制备了具有柱状晶结构的Gd掺杂CeO2(GDC)薄膜，通过溶胶涂覆结合热扩散处理，沿薄膜柱状晶界面分别扩散了Fe元素和Si元素，研究了不同元素扩散掺杂对GDC薄膜电导行为的影响。结果表明：GDC薄膜具有典型的柱状晶结构，扩散掺杂元素前后GDC薄膜均为立方萤石结构，且沿（111）面择优生长；经不同退火温度处理后GDC薄膜晶粒尺寸在10 nm到100 nm之间，扩散掺杂Fe元素能显著提高薄膜的电导率。在800℃退火条件下薄膜电导率显著提高，电导激活能没有改变。掺杂Fe元素可以改变晶界处硅质相的润湿性，使晶界处的硅质相收缩在三个晶粒交界处，从而提高GDC薄膜的电导率。本研究分析并建立了异价掺杂离子对CeO2基电解质电导率的影响机制，揭示了不同价态离子对晶界空间电势及界面区杂质相的作用规律，确立了通过界面区离子掺杂改善CeO2基电解质导电行为的工艺途径。本项目将为改善CeO2基电解质的电导特性、拓展其应用范围探索新的途径并奠定相应的理论基础。