Investigation of MIEC Materials Using an Amperometric Oxygen Titration Method

Abstract

For any mixed ionic-electronic conducting (MIEC) oxide an assess¬ment of its basic material properties should include chemical stability as a function of oxygen partial pressure pO2. However, the stability range is not always easily experimentally accessible. Using a closed tubular zirconia "oxygen pump" setup with platinum electrodes facilitates precise control of the oxygen partial pressure in the enclosed volume within the whole pO2 range between 10-20 ... 1 bar at temperatures above 700 °C. By measuring the electric current necessary for pumping oxygen into or out of the sample chamber, the amount of oxygen transported can be determined with a high precision. In this way, the oxygen uptake or release of an oxide powder sample is determined as a function of pO2, temperature and time, yielding information on stoichiometry changes and the stability limits of an MIEC oxide.