Influence of the kinds of aluminum source on the preferential orientation and properties of Naβ-alumina ceramics

Nuβ-alumina is a two-dimensional ionic conductor in which insulating spinel layers separate conducting planes of Na⁺ ions. Naβ-alumina ceramics is expected to be used as solid electrolytes because it is strong ionic conductor and mechanically reliable. Therefore, we prepared c-plane-oriented Naβ-alumina ceramics from three aluminum sources using a hot-pressing method and evaluated their ionic conductivity and mechanical strength. In all samples, the ionic conductivity perpendicular to the pressing direction was ten times greater than in the parallel direction. The mechanical strength parallel to the pressing direction was 1.5 times larger than that in the perpendicular direction. The samples made from a mixture of 50 mol% platelike gibbsite and 50 mol% spherical alumina showed the maximum preferential orientation with favorable relative density.