AC Impedance Investigation of Samarium-Doped Ceria

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Abstract
The electrical conductivity of sintered samples of (CeO2)1−x(SmO1.5)x(CeO2)1−x(SmO1.5)x (0.10⩽x⩽0.40)(0.10⩽x⩽0.40) in air was investigated systematically as a function of temperature between 240 and 1000°C by using two-probe ac impedance technique. The relative contribution of the grain interior (lattice) and grain boundaries to the overall resistance, is discussed in detail in relation with the grain boundary effect. The maximum lattice conductivity observed (at 600°C) was 2 S/m for Ce0.9Sm0.1O1.95.Ce0.9Sm0.1O1.95. With an increase in samarium concentration, the grain interior conductivity decreases gradually, but the grain boundary conductivity increases dramatically. The two opposite effects lead to a maximum (σt,600°C(σt,600°C = 1 S/cm) in the overall conductivity at x=0.2.x=0.2. A linear relationship between the association enthalpy of the defect cluster, [SmCe′−VO••],[SmCe′−VO••], and x1/3x1/3 was proposed. © 2001 The Electrochemical Society. All rights reserved.