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

Abstract

A few compositions in the system Ce 1-xSr xO 2-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 °C for 4 h. Solid solution has formed in the composition with x = 0.05. All other compositions have been found to contain XRD lines of SrCeO 3 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 O 2- 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 × 10 -3 S cm -1 at 500 °C among the series. Ionic conductivity decreases gradually with increasing x. This is due to the formation of a second phase SrCeO 3 and increasing probability of formation of neutral associated defect pairs, S r′′ Ce-VO. © 2011 Elsevier B.V. All rights reserved.