Solid oxide fuel cells employ a similar operation mechanism to ceramic oxygen sensors and generators, consisting of two porous electrodes separated by a dense, oxygen conducting electrolyte. The high oxygen ion conductivity of Yttrium stabilized Zirconia (YSZ) over wide ranges of temperature and oxygen pressures has led to its use as an electrolyte in solid oxide fuel cells (SOFCs). These cells employ Yttrium stabilized Zirconia as an electrolyte through which the oxide ions O2- migrate from the air electrode (cathode) side to the fuel electrode (anode) side, where they react with the fuel (H2, CO, etc) to generate an electrical voltage in a clean and highly efficient way. Yttrium stabilized Zirconia is the most effective electrolyte tested.