Measurement and control of oxygen fugacity by means of gaseous oxygen buffers

Sammanfattning: Fundamental and practical aspects of oxygen buffering are reviewed, with particular reference to the gaseous oxygen buffer as a tool in elevated temperature oxide chemistry. An oxygen buffer capacity concept and a classification scheme for oxygen buffers are proposed; their application is demonstrated. The use, and limitations, of solid electrolyte oxygen gauges and pumps in the gaseous oxygen buffer context are examined; polarization and thermal asymmetry effects are calculated. Various forms of interaction between gaseous and condensed oxygen buffers are exemplified. The author's contribution to die methodology of circulating oxygen buffer atmospheres is summarized. The available data on the equilibrium thermodynamics of nickel + nickel oxide, a common reference buffer, are evaluated; its equilibrium oxygen fugacity appears to be slightly but significantly affected by direct contact with stabilized zirconia. Preparative work in the vanadium - oxygen and tungsten - oxygen systems is put into perspective against a brief structural background.