The oxygen nonstoichiometry, the total conductivity, and the electronic conductivity of [(ZrO2)0.8(CeO2)0.2] 0.9(CaO)0.1 were measured by using high temperature gravimetry, dc four-terminal method, and Hebb-Wagner's dc polarization technique, respectively. The change in the oxygen nonstoichiometry was explained by assuming Ce′Zr, Ca″zr, and VO•• as major defects. At 1173 K and pO2 = 1 ∼ 10-11 atm, the total conductivity corresponded to the ionic conductivity is proportional to [VO••]. At the lower p02, although the oxygen vacancy increased with the decreasing pO2, the ionic conductivity decreased. The relation between [VO••] and the ionic conductivity was similar to that in stabilized ZrO2 with various CaO contents. It was shown that the electronic conductivity is proportional to [Ce′Zr, which is not in accordance with the hopping-type conduction between Ce3+ and Ce4+. Assuming all Ce′Zr release conduction electrons, the calculated mobility is in the order of 10-6 cm2 V-1 s-1 at 1173 K and does not correspond to the band conduction model. It was considered that most of the electrons are trapped at the donor level formed by Ce′Zr and only a small portion of the electrons is excited to conduction band as carriers.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry