The relation between microstructure and ionic conductivity of hot-pressed β-Al₂O₃

The microstructure variation of β-Al₂O₃ with different compositions during hot-pressing and its effect on ionic conductivity were studied. It is found that, besides the phase composition, the conductivity of hot-pressed β-Al₂O₃ materials of the same composition is also related to the measurement direction, microstructure and density. The resistivity in the direction parallel to hot-pressing is about three times higher than that perpendicular to the hot pressing. The pores in the material are particularly detrimental to the ionic conduction. It was observed that the shape of complex impedance plane spectrum changed with measurement temperature and such change was affected by chemical composition and sample preparation condition. This phenomenon is explained successfully with the help of the ideal equivalent circuit of polycrystalline fast ionic conductor and the results of the conductivity measurement of hot-pressed β-Al₂O₃.