Electrical Properties and Defect Structure of a (0.13YO _1.5 ·0.87ThO ₂ ) Electrolyte

Abstract

High‐density sintered disks of the composition 0.13YO 1.5 ·0.87ThO 2 are shown to be mixed conductors at high oxygen pressures (>10 −6 atm) by electrical conductivity and electrochemical cell measurements. The ac and dc conductivity measurements were made between 900° and 1600°C over a wide range of oxygen partial pressures. A blocking‐electrode polarization technique for determining transference numbers was not applicable at high oxygen pressures but appeared to work at the lower pressures, indicating a transition to n ‐type behavior. The electrochemical cell measurements show essentially completely ionic behavior at low oxygen pressure but indicate at least 0.1% electronic contribution at 10 −13 atm at 1000°C. The lower oxygen pressure limit for completely ionic behavior has not been determined but extends below the equilibrium pressures of an Mn‐MnO 2 , Cr‐Cr 2 O 3 electrochemical cell at 1000°C.