Role of space charge in the grain boundary blocking effect in doped zirconia

Although the presence of siliceous phases is a major cause of the grain boundary blocking effect in doped zirconia (ZrO2), the grain boundary resistivity also appears to be significantly influenced by space charges. The ionic transport across the grain boundaries occurs solely through direct grain-to-grain contacts which are themselves blocking in nature. Such a blocking effect can be consistently accounted for by the oxygen vacancy depletion in the grain boundary space charge layer. The Al2O3 addition markedly modified the grain boundary properties, which are also consistently explained by the space charge effect.