Oxygen Potential Measurement of Americium Oxide by Electromotive Force Method

The oxygen potentials of AmO2−x were measured in the x range of 0.01–0.5 and the temperature range of 1000–1333 K by the electromotive force method. The oxygen potentials at 1333 K were −19.83 kJ/mol for x=0.019 and −319.1 kJ/mol for x=0.485, which were higher than those of CeO2−x by approximately 200 kJ/mol for the corresponding x values. From the dependence of the oxygen potentials on x and temperature, a tentative phase diagram of Am–O system was proposed, which suggested the presence of the intermediate phases of Am7O12 and Am9O16 in the Am–O system.