High-Temperature Transference Number Determinations by Polarization Measurements

A polarization technique for the measurement of electronic and ionic transference numbers in mixed conductors is described; also a discussion of the conditions governing its applicability. The application of this technique is demonstrated by measurements on the solid solution Zr0.85 Ca0.15 O1.85, which is shown to be intrinsically a pure oxygen ion conductor even at room temperature at an oxygen partial pressure of 10−9 atm. The electronic conductivity in this material can be increased significantly at low oxygen partial pressures by the addition of transition metal impurities.