Effect of strontium (Sr) doping on the conductivity of ceria

A few compositions in the system Ce1-xSrxO2-x, with 0.05 <= x <= 0.20 have been prepared by auto-combustion method. More than 93% of theoretical density has been achieved by sintering at 1350 degrees C for 4h. Solid solution has formed in the composition with x = 0.05. All other compositions have been found to contain XRD lines of SrCeO3 beside the major fluorite phase. Complex plane impedance analysis has clearly revealed the contribution of grains, grain boundaries, and electrode specimen interface to the total observed resistance of the sample. Conduction occurs mainly due to diffusion of O2- ions through oxygen vacancies as indicated by values of activation energy of conduction. Composition, Ce-0.95 Sr-0.05 O-1.95 exhibits the highest ionic conductivity 3.26 x 10(-3) S cm(-1) at 500 degrees C among the series. Ionic conductivity decreases gradually with increasing x. This is due to the formation of a second phase SrCeO3 and increasing probability of formation of neutral associated defect pairs, Sr'' ce - V-o(center dot center dot). (C) 2011 Elsevier B.V. All rights reserved.