Electrical properties of calcia-stabilised zirconia ceramics : voltage-induced p-type conductivity and oxygen redox activity

The electrical properties of oxide ion-conducting Ca0.15Zr0.85O1.85, CSZ, ceramics were investigated using impedance spectroscopy as a function of temperature and applied dc bias. The total resistance showed a time-dependent decrease during application of a dc bias and was attributed to the reversible introduction of p-type semiconductivity, initially at the sample surface followed by grain boundaries and the sample bulk. Electron holes may be located on under-bonded oxygen ions which are associated either with Ca dopant ions or the ceramic surfaces and interfaces, resulting in mixed oxide ion and p-type electronic conduction. This p-type behaviour with a dc bias is different from the behaviour of most well-studied, stabilised zirconias which become n-type mixed conducting due to oxygen loss at low pO2.