A thermodynamic and electrical conductivity study of nonstoichiometric cerium dioxide

Thermodynamic and dc electrical conductivity measurements were performed on nonstoichiometric CeO_2?x to characterize the electrical behavior and defect structure in the vicinity of the n to p transition. Using the mass action approach, activation energies of 2.57, 1.15 and 0.63 eV were obtained for the electron, hole and ionic partial conductivities respectively (600–1000°C, 1<P_o2<10^?4 atm). Thermodynamic measurements of 99.99%CeO_2-x by electrochemical coulometric titration yielded expressions for point defect concentrations per cm³ and nonstoichiometry in the impurity dominated region at 800°C as follows:

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. Thermodynamic constant composition measurements revealed a decrease in the partial molar enthalpy (from - 10 eV) with decreasing stoichiometry for x<10^?2.8. This decrease is attributed to defect reaction involving both holes and electrons.