Oxidation and Equilibrium in Nonstoichiometric Zirconium Dioxide Powder

Two properties of nonstoichiometric zirconium dioxide powder have been studied. Pressures of oxygen in equilibrium with , with 0.03 > x > 0, have been determined at temperatures of 900°, 1000°, and 1100°C by passing hydrogen‐water vapor mixtures over the oxide. The measured pressures are in the range 10 −20 to 10 −12 atm. Rates of oxidation of in oxygen have been measured at 500°–650°C. The activation energy for the oxidation, based on a diffusion mechanism, is 58.0 kcal/mole. A comparison of the rates of oxidation of with the rates of oxidation of zirconium metal indicates that different mechanisms are operative.