US5001021-A  Ross, P. N. and Benjamin, T. G., "Thermal Efficiency of Solid Electrolyte Fuel Cells with Mixed Conduction", Journal of Power Sources 1 (197677).;  Tuller, H. L. and Norwick, A. S., "Doped Ceria as a Solid Electrolyte", Journal of the Electrochemical Society: Solid State Science, vol. 122, No. 2,225 (Feb. 1975).WO9109430-A  See also references of EP 0504260A1WO9109430-A3  Chemical Abstracts, volume 103, no. 6, August 1985, (Columbus, OH, US), T. Ivers-Tiffee et al.: "Electrical behavior of doped ceria", page 154, abstract 39819u & Silic. Ind. 1984, 49(11-12), 227-230;  Extended Abstracts Fall Meeting, Honolulu, Hawaii, 18/10/1987-23/10/1987, volume 87, no. 2, H. Arai et al.: "High temperature fuel cell with ceria-based solid electrolyte", pages 263-264, abstract no. 179;  Extended Abstracts, volume 75, no. 1, May 1975, abstract no. 46, A.S. Nowick et al.: "Oxygen-ion conductivity in oxides of the fluorite structure", pages 98-99;  Journal of the Electrochemical Society, volume 126, no. 2, February 1979, R.T. Dirstine et al.: "Ionic conductivity of calcia, yttria, and rare earth-doped cerium dioxide", pages 264-269;  Solid State Ionics, volume 5, 1981, North Holland Publishing Co. (NL), R. Gerhardt-Anderson et al.: "Ionic conductivity of CeO2 with trivalent dopants of different ionic radii", pages 547-550;  Journal of the Electrochemical Society, volume 122, no. 1, January 1975, T.Kudo et al.: "Oxygen ion conduction of the fluorite-type Ce1-xLnxO2-x/2", pages 142-147EP504260-B1  Chemical abstracts, vol. 103, no. 6, Aug. 1985, (Columbus; Ohio, US), T. Ivers-Tiffee et al.: "Electrical behavior of doped ceria", page 154, abstract 39819u;  Extended Abstracts Fall Meeting, Honolulu, Hawaii, 18/10/1987-23/10/1987, vol. 87, no. 2, H. Arai et al.: "High temperature fuel cell with ceria-based solid electrolyte", pages 263-264, abstract no. 179;  Extended Abstracts, vol. 75, no. 1, May 1975, abstract no. 46, A.S. Nowick et al.: "Oxygen-ion conductivity in oxides of thhe fluorite structure", pages 98-99;  Journal of the Electrochemical Societey, vol. 122, no. 1, Jan. 1975, T. Kudo et al.: "Oxygen ion conduction of the fluorite-type Ce1-xL-nx02-x/2", pages 142-147;  Journal of the Electrochemical Society, vol. 126, no. 2, Feb. 1979, R.T. Dirstine et al.: "Ionic conductivity of calcia, yttria, and rare earthdoped cerium dioxide", pages 264-269;  Silic. Ind. 1984, 49(11-12), 227-230;  Solid State Ionics, vol. 5, 1981, North Holland Publishing Co. (NL), R. Gerhardt-Anderson et al.: "Ionic conductivity of Ce02 with trivalent dopants of different ionic radii", pages 574-550;  Journal of the Electrochemical Societey, vol. 122, no. 1, Jan. 1975, T. Kudo et al.: "Oxygen ion conduction of the fluorite-type Ce1-xLnx02-x/2", pages 142-147, see page 143, left-hand column, 3rd paragraph; table 1; page 144, left-hand column, 4th para.;  Extended Abstracts Fall Meeting, Honolulu, Hawaii, 18-23 October 1987, vol. 87, no. 2, H. Arai et al.: "High temperature fuel cell with ceria-based solid electrolyte", pages 263-264, see abstract no. 179;  Chemical abstracts, vol. 103, no. 6, Aug. 1985, (Columbus; Ohio, US), T. Ivers-Tiffee et al.: "Electrical behavior of doped ceria", see page 154, abstract 39819u & Silic. Ind. 1984, 49(11-12), 227-230;  Journal of the Electrochemical Society, vol. 126, no. 2, Feb. 1979, R.T. Dirstine et al.: "Ionic conductivity of calcia, yttria, and rare earth-doped cerium dioxide", pages 264-269;  Extended Abstracts, vol. 75, no. 1, May 1975, abstract no. 46, A.S. Nowick et al.: "Oxygen-ion conductivity in oxides of the fluorite structure", pages 98-99