复合相基体上制备的beta-氧化铝膜及其特性

Preparation and Characteristics of Beta-alumina Films on α-Alumina and Its Composite Substrate

研究了在α-Al_2O_3及其与尖晶石复合的陶瓷基体上多晶Na-beta-Al_2O_3膜的形成过程及其特性.结果表明,在单相α-Al_2O_3基体上形成的beta-Al_20_3膜呈现不均匀的显微结构,异常长大的晶粒尺寸达到15μm.在复合相基体上制备的Na-beta-Al_2O_3膜晶粒尺寸得到了有效的控制,当其中相应的MgO含量为3wt％时,Na-beta-Al_2O_3的晶粒异常生长被完全抑制,最大晶粒尺寸仅2～3μm.动力学分析表明,复合基体表面Na-beta-Al_2O_3(Li,Mg)的形成过程中,Li的扩散和α-Al_2O_3→尖晶石的结构重排同时控制膜的生长过程.所制备的beta-Al_2O_3膜的钠离子导电性与beta-Al_2O_3陶瓷体相似,并取决于其中β-Al_2O_3和β″-Al_2O_3相的相对含量以及过剩MgAl_2O_4的含量.

Beta-Al2O3 structured ionic conductors, involving β- and β'- Al2O3 phases, are among the most favorable solid electrolyte materials for electrochemical sensors because of their excellent ionic conductivity and chemical stability. Usually they are used in tube or disc forms. Microcrack-free beta-Al2O3 films on α-Al2O3 or its composite ceramic substrates were obtained by the surface reaction of the substrate with lithium and sodium component from beta-Al2O3 atmosphere. SEM results show heterogeneous microstructures of the beta-Al2O3 film, with some overgrown grains as large as 15μm. The addition of MgAl2O3 spinel phase in the α-Al2O3 substrate effectively improves the morphology of the films with maximum grain size of 2-3μm. The kinetic processes of the Na-beta-Al2O3 (Li,Mg) film formation on composite substrate are controlled by both the lithium transportation velocity and the rearrangement of α-Al2O3 to spinel structure of beta-Al2O3- Impedance analyses indicate that the beta-Al2O3 films obtained possess comparable electrical properties to those of ceramic blocks and depend on the relative contents of β- and β'-Al2O3, and obey the Arrehnius relationship.