Summary

In this module, we discussed the defect formation in ceramic, with references to oxides. While defects such as Schottky defects maintain the stoichiometry of the materials, most oxide ceramics are prone to the non-stoichiometry. This non-stoichiometry results in defects such as ion vacancies or interstitials and compensating charged defects either via ionic compensation or electronic compensation. While defect concentration in the intermediate oxygen partial pressure (around atmospheric conditions) are independent of the partial pressure of oxygen, the defects in non-stoichiotemetric oxides either at high or low pressures are strongly dependent on the partial pressure of oxygen. This can be effectively understood through the construction of Brower diagrams. Finally, we looked at the electronic disorder and evaluated the conditions to compare the ionic and electronic defect concentrations.