Electrical Conductivity of Ceria-Based Oxides/Alkali Carbonate Eutectic Nanocomposites

Abstract

Differential thermal analysis (DTA) and electrical conductivity calculated from AC impedance measurements are discussed for binary and ternary eutectics: (Li 0.52 Na 0.48 ) 2 CO 3 (LN) and (Li 0.435 Na 0.315 K 0.25 ) 2 CO 3 (LNK), coexisting with nanosized CeO 2 and ceria-based oxides such as CeO 2 :Sm 3+ (samarium doped ceria: SDC) particles prepared by the Pechini method. The influence of the surface properties of oxides with smooth surfaces, narrow particle size distributions, and large specific surface areas near the eutectic point is presented. The obtained DTA spectra indicate that the melting enthalpy disappeared in systems with a melt containing less than 30 vol% and 45 vol% LN and LNK eutectics, respectively. Sm 3+ doping contributes to an increase in the electrical conductivity of the composites below the eutectic points of molten carbonate. The temperature dependence of the electrical conductivity for both binary and ternary eutectic carbonates coexisting with CeO 2 and SDC at melt contents less than ca. 15 vol% does not indicate a remarkable change in conductivity in the temperature range near each eutectic point of molten carbonate. The low-temperature characteristics are significantly improved using nanosized ceria-based oxides because of non-frozen eutectics with a low molar enthalpy of fusion and limited solid-phase influence on ionic conduction.