Fabrication of oriented β-alumina from porous bodies by slip casting in a high magnetic field

Designing texture is one possible way for improving the electrical, chemical, mechanical and other properties of ceramics. We have reported that oriented α-alumina was obtained by slip casting in a high magnetic field followed by sintering. β-Alumina is well known as sodium ion conductor used in a sodium-sulfur battery. β-Alumina consists of spinel blocks and ion conductive planes. Since the direction of the ion conductive plane of polycrystalline β-alumina is random, the ionic conductivity of the polycrystal is lower than that of the single crystal. The purpose of this study is to prepare oriented β-alumina to enhance the sodium ion conductivity. Oriented β-alumina was prepared by the following method: (1) oriented α-alumina green bodies were prepared by colloidal processing in a high magnetic field, (2) the oriented α-alumina green bodies were infiltrated with Na₂O and MgO, and (3) the oriented β-alumina bodies were synthesized by reaction sintering at 1600 and 1700 °C. The reaction product and orientation of the β-alumina were confirmed by XRD.