Electric properties of [(ZrO₂)_0.8(CeO₂)_0.2] _0.9(CaO)_0.1 solid solution

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 V_O^•• as major defects. At 1173 K and p_O2 = 1 ∼ 10^-11 atm, the total conductivity corresponded to the ionic conductivity is proportional to [V_O^••]. At the lower p₀₂, although the oxygen vacancy increased with the decreasing p_O2, the ionic conductivity decreased. The relation between [V_O^••] 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.