Electrical properties of Mg-doped and Mg, Si co-doped alumina

Impedance measurements on Mg-doped alumina ceramics, over the temperature range 400−910 °C, showed a combination of oxide ion conductivity and p-type electronic conductivity, depending on temperature and oxygen partial pressure. The oxide ion conductivity is attributed to oxygen vacancies, introduced as charge compensation for the Mg dopant. The p-type conductivity is attributed to hole creation on under-bonded oxide ions and is the dominant conductivity for measurements in air at high temperatures. In samples co-doped with Mg and Si, impedance measurements showed a reduction in oxide ion conductivity and therefore, number of oxide ion vacancies because the self-compensation mechanism of co-doping lead to direct replacement of Al3+by Mg2+ and Si4+; the level of p-type conductivity was also reduced.