A zirconia-yttria-niobia solid solution phase with a fluorite structure was prepared. The electrical properties were investigated by using powder X-ray diffractometry and 2-probe alternating-current conductivity. The electrical conductivity was studied as a function of temperature, O partial pressure and annealing time. The trivalent- and pentavalent-substituted zirconia system permitted a qualitative interpretation to be made of the variation in conductivity as a function of composition. In the range of fluorite-phase solid solutions, it was found that the activation energy for conduction was the predominant factor which governed the conduction behavior, rather than the concentration of O-ion vacancies. The maximum conductivity was found to occur near to the minimum concentration of dopant which was required in order to stabilize the fluorite phase.

Phase Relationship and Electrical Conductivity in the ZrO2-Y0.75Nb0.25O1.75 System. J.H.Lee, M.Yoshimura: Solid State Ionics, 2001, 139[3-4], 197-203