Microstructural development and oxygen ion mobility in Sr, Ba, and Ca-doped LaAlO3 perovskites

ABSTRACT Perovskite-type materials have been extensively investigated in the attempt to find new electrolyte materials for Solid Oxide Fuel Cell that work at low temperatures. Among these materials, LaAlO3 stands out for presenting considerable ionic conductivity when adequately doped. In this work, pure and Sr, Ba, and Ca-doped LaAlO3 were studied. The powders were prepared by solid state reaction. Microstructural, structural and electrical conductivity of sintered samples were analyzed by scanning electron microscopy, X-ray diffraction and impedance spectroscopy, respectively. Among the different kinds of dopants, Sr-doped sample presented the higher conductivity, for both the grain ( at 800°C) and total ( at 800°C) conductivity. In all doped samples, the total conductivity is controlled by the grain boundary, i.e., the grain boundary is more resistive than the grain, and the microstructures are heterogeneous and the degree of heterogeneity is determined by the dopant.摘要 钙钛矿型材料已被广泛研究，旨在探寻适用于低温运行的固体氧化物燃料电池（Solid Oxide Fuel Cell）的新型电解质材料。在这类材料中，铝酸镧（LaAlO₃）经适当掺杂后可表现出可观的离子电导率，因而脱颖而出。本研究针对纯相以及锶（Sr）、钡（Ba）、钙（Ca）掺杂的铝酸镧展开探究。粉体采用固相反应法制备。分别通过扫描电子显微镜（Scanning Electron Microscopy）、X射线衍射（X-ray Diffraction）与阻抗谱（Impedance Spectroscopy）对烧结样品的微观结构、物相结构及电导率进行表征。在各类掺杂剂中，锶掺杂样品的晶粒电导率（800℃下）与总电导率（800℃下）均为最高。所有掺杂样品的总电导率均由晶界主导，即晶界电阻高于晶粒本体；且样品微观结构呈非均质性，其非均匀程度由掺杂剂种类决定。