Lattice Oxygen Transfer in Fluorite-Type Oxides Containing Ce, Pr, and/or Tb

Oxygen transfer capacity (OTC) is needed, for example, in three-way catalysts (TWC) for treatment of exhaust gases, extraction of pure oxygen from gaseous mixtures such as air, or the extraction of hydrogen from hydrogen-containing compounds such as water or methane. This property is explored in fluorite-related materials of the formula Ce1-x-y-z-pPrxTbyMzRpO2x (x+y+z>0.5) in which M is a metal, especially Zr, Ti, V, Mo, W, Nb, Mn, Cu, Cr, Fe, Ni, Co, Ta, and Bi, and in which R is another rare-earth element. The OTC of these oxides is inherent in the characteristics of fluorite-related structures and the variable valency of Ce, Pr, and/or Tb. Such oxides can have the OTC property under reducing and oxidizing conditions without any reconstructive phase transitions. OTC data of some binary, ternary, and quaternary oxides containing Ce, Pr, or Tb are discussed.