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The direct current‐voltage characteristics of symmetrical cells Pt, O2(I), |Zr0.85Ca0.15O1.85|normalPt , O2(II), with pO2false(Ifalse)=pO2false(IIfalse) , were measured at 560°C under oxygen pressures from 1 to 10−20 atm. The characteristics were nonohmic, the deviation from ohmic law being mainly due to the potential drop at the cathode interface between the solid electrolyte and the gas ambient. The characteristics consist of two parts. The first is characterized by a marked oxygen pressure dependence and is observed at voltages lower than approximately 2V (weak polarization). In this range, the rate‐determining process is the diffusion of oxygen atoms (resulting from dissociation of O2 or H2O ) through the platinum of the Pt paste electrode. The second part of the characteristic is almost independent of the oxygen pressure and is observed at voltages higher than approximately 2V (strong polarization). Here the rate‐determining step is the process in which neutral oxygen atoms, adsorbed at the cathode surface of the electrolyte, combine with effectively neutral oxygen vacancies VOx , (oxygen ion vacancies which have trapped two electrons) to form a normal O2− lattice ion false(OOxfalse) . This process utilizes the part of the electrolyte surface not in contact with the platinum, but close to points where the platinum makes contact, and involves migration of electrons from the platinum over the surface of the electrolyte.

Structural images of the stacking faults in β‐SiC were obtained with a high‐resolution electron microscope. Stacking faults initially present in β‐SiC powder particles were eliminated as grain growth proceeded at elevated temperatures.

The electrical resistivity of ZnO doped with Al2O3 was measured in air and under reduced pressure (∼0.5 mm Hg) in the range from 30° to 680°C as a function of the degree of sintering. The data obtained were explained in terms of the effects of the microstructure of the sintered body and the chemisorbed oxygen. There are two mechanisms of electrical conduction involved, only one of which is affected by the microstructure.

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