Solid solutions were formed in the La₂O₃-Cao and Y₂O₃-Cao systems via an oxalate coprecipitation method. Electrical measurements were taken on pellets about 1/2 in. in diameter and 1/8 in. thick, prepared by pressing the oxides at about 100,000 psi and sintering at .1600°c.

At 1600°C, La₂O₃ can dissolve about 16 mole % Cao which leads to the creation of anion vacancies. No compounds are formed in this system. The electrical conductivities of pellets containing from 0 to 50 mole % CaO were measured at 400°-1100°C under oxygen pressures varying between 1 and 10207b ²¹ atm at 1000°C. The defect solid solutions behave as oxygen anion conductors below an oxygen pressure of 10⁻⁷ atm. The maximum ionic conductivity, which is 2.4 x 10⁻² ohms⁻¹cm⁻¹ at 1000°C, was observed at a composition coinciding with the solubility limit. At high oxygen pressures, the appearance of p-type conductivity, proportional to P_O₂^1/4, results in a region of mixed conduction. The apparent activation energies for both ionic and p-type conduction are in the neighbourhood of 17-20 kcal/mole. N-type conductivity was not observed at low oxygen pressures. Even La₂O₃ exhibits predominantly ionic conduction at intermediate oxygen pressures. Several transport numbers were verified by emf measurements on galvanic cells with Cu-Cu₂O, Ni-NiO, Fe-Fe_xO, and Cr-Cr₂O₃ electrodes.

Only 5 to 8 mole % Cao could be dissolved in Y₂O₃ at 1600°C. The solid solutions are solely ionic conductors only below an oxygen pressure of about atm. The ionic conductivities are almost two orders of magnitude lower 10⁻¹² than those exhibited by the La₂O₃-Cao electrolytes. Again, the p-type conductivity at high oxygen pressures varied as P_O₂. Since the apparent activation energies for ionic and p-type conduction are in the vicinity of 25-30 and 36 kcal/mole, respectively, ionic transport numbers decrease with increasing temperature. The ionic contribution to the conductivity of Y₂O₃ is very small.

The behaviour of impervious ZrO₂ + 10 mole %. Cao electrolyte tubes was studied at 500°-1100°C in oxygen concentration cells of the type (-) Aг-O₂ or CO-CO₂/ZrO₂-C2O/O₂ (+). The equilibrium oxygen pressures imposed by Ar-O₂ (1-10⁻⁶ atm) and CO-CO₂ (10⁻⁶-10⁻¹⁸ atm at 1000°C) mixtures were determined. For Ar-O₂ mixtures, the oxygen pressures can be measured with accuracies of ±0.4% at 1-10⁻² atm and ±4% at 10⁻⁴-10⁻⁵. atm. An accuracy of ±11% can be achieved with CO-CO₂ mixtures. The emf's of the above cell increase as the gas flow rate increases at low flow rates and then become independent of flow rate at high flow rates. The minimum flow rates required to eliminate any significant flow rate dependence are given as a function of oxygen pressure..

When currents are passed through the oxygen concentration cell, only resistance polarization is generally observed in the presence of Ar-O₂ mixtures, even at current densities of 250 ma/cm² and 1000°C. If Ar-O₂ mixtures dilute in O₂ are present at the cathode, concentration polarization arises. Limiting currents, proportional to P_O₂ are controlled by the diffusion of oxygen through the gas phase to the reaction sites. When the oxygen pressure at the cathode is reduced to 10^-27.5 atm at 1000°C, a significant amount of electronic conductivity is introduced into the electrolyte. For CO-CO2₂ mixtures, activation polarization was detected. Exchange current densities are about 1 ma/cm² 850°-1100°C.

The polarization behaviour of the cell (-) Ar-O₂,O(in Ag)/ZrO₂-CaO/O₂ (+) where O represents dissolved oxygen was investigated at 1000°-1200°C. When voltages are applied to the cell to reduce oxygen in the liquid silver, limiting currents, controlled by the diffusion of oxygen in the melt, can be observed. The limiting currents are directly proportional to the concentration of dissolved oxygen (or P_O₂^1/2) from 0.01 to 2.0 atomic % oxygen. This technique could be used to analyze liquid metals for dissolved oxygen.