In situ control of oxygen fugacity at high temperature and high pressure

A new technique to control oxygen fugacity in situ under high-temperature a nd high-pressure conditions has been developed. In this method a special sa mple assembly constructed of a reference buffer, yttrium-stabilized zirconi a (YSZ)disks, a sample, and an oxygen reservoir was used. Through a driving voltage epsilon(0) between the sample and the oxygen reservoir, oxygen was moved from the reservoir into the sample, or from the sample into the rese rvoir. The rate of oxygen transport was adjusted by regulating epsilon(0) a nd the thickness of the YSZ disk d(0). The oxygen fugacity in the sample an d its variation during the process were monitored in situ by measuring the voltage between the sample and reference buffer. Tn this way the oxygen fug acity in the sample was controlled independently of temperature, pressure, and composition of the sample. We made experiments at 773-994 K and 1.0-4.0 GPa in the systems Cu-O, C-O,and Ni-O, and the results show that the techn ique is successful.