Higher conductivity Sm3+ and Nd3+ co-doped ceria-based electrolyte materials

A co-doping strategy is used to enhance the ionic conductivity of doped cefia. Recent density functional theory has suggested that Pin with atomic number 61, is the ideal dopant exhibiting low activation energy for oxygen diffusion, and consequently high ionic conductivity. Taking the atomic number of Pm3+ into account, Sm3+ and Nd3+ are selected as co-dopants for ceria to test this hypothesis. Different compositions of Smx/2Ndx/2Ce1-x O2-delta(x=0.01-0.20) are synthesized using conventional solid state route. The lattice parameters are estimated after the detailed analysis of X-ray diffraction data using least-squares extrapolation technique. The lattice parameter in Smx/2Ndx/2Ce1-xO2-delta system obeys Vegard's law, even a thigher dopant concentration, indicating that short-range oxygen vacancy ordering is comparatively lower than in other systems. The ionic conductivity of the samples is measured in the temperature range of 250 degrees C to 700 degrees C, using two-probe electrochemical impedance spectroscopy technique. The grain contribution to the ionic conductivity for Smx/2Ndx/2Ce1-xO2-delta is discussed in detail. The grain ionic conductivity Of Sm0.075Nd0.075Ce0.85O2-delta 6 is found to be 30% higher than that of Gd0.10Ce0.9O2-delta at 550 degrees C. It is shown that Smx/2Ndx/2Ce1-xO2-delta is an electrolyte that obeys the Meyer-Neldel rule. In the high temperature (> 475 degrees C) region, the activation energy shows a minima at 5 mol% dopant concentration with the value of 0.62 ev. Published by Elsevier B.V.