Solid state electrochemical techniques for studies on nonstoichiometry and defect structure of metal oxides

The equilibrium oxygen partial pressures of several nonstoichiometric oxides were determined as a function of composition and temperature. The defect structures of nonstoichiometric phases are discussed. Thermodynamic properties of UO2+x were determined by using a stacked pellet-type cell and the variation of Δ bar SO2 with x was explained on the basis of the 2:2:2 Willis model. The phase relations and nonstoichiometry in V2O5-x, LiVO3-x, BaBiO3-x, PrOx and Ba2HoCu3O7-y were studied by coulometric titration and the results are discussed on the basis of the mass-action law and statistical models. The electrical conductivity measurements were made under the condition of constant oxygen content or temperature in-situ using a modified coulometric titration technique. Coulometric titration has proved to be very useful to study the phase relations particularly in the oxides with small deviations from the stoichiometric composition