Crystal Structure–Ionic Conductivity Relationships in Doped Ceria Systems

Abstract

In the past, it has been suggested that the maximum ionic conductivity is achieved in ceria, when doped with an acceptor cation that causes minimum distortion in the cubic fluorite crystal lattice. In the present work, this hypothesis is tested by measuring both the ionic conductivity and elastic lattice strain of 10 mol% trivalent cation‐doped ceria systems at the same temperatures. A consistent set of ionic conductivity data is developed, where the samples are synthesized under similar experimental conditions. On comparing the grain ionic conductivity, Nd0.10Ce0.90O2−δ exhibits the highest ionic conductivity among other doped ceria systems. The grain ionic conductivity is around 17% higher than that of Gd0.10Ce0.90O2−δ at 500°C, in air. X‐ray diffraction profiles are collected on the sintered powder of all the compositions, from room temperature to 600°C, in air. From the lattice expansion data at high temperatures, the minimal elastic strain due to the presence of dopant is observed in Dy0.10Ce0.90O2−δ. Nd0.10Ce0.90O2−δ exhibits larger elastic lattice strain than Dy0.10Ce0.90O2−δ with better ionic conductivity at intermediate temperatures. Therefore, it is shown that the previously proposed crystal structure–ionic conductivity relationship based on minimum elastic strain is not sufficient to explain the ionic conductivity behavior in ceria‐based system.

A CO2-stable reduction-tolerant Nd-containing dual phase membrane for oxyfuel CO2capture

“…Fe-doped Ln (Ln ¼ La series elements) SrO 3 ) are reported to show a higher stability than Co/Ni-based oxides under a reducing or CO 2 atmosphere 26 and show good p-type electronic conductivity; 27,28 (ii) in a recent study, covering a large number of 10 atm% rare earth doped cerias, synthesized under similar conditions, Nd-doping ceria is reported to exhibit the highest ionic conductivity. 29 (iii) Based on the common ion effects, which was dened as the suppression of dissociation of a weak electrolyte containing a common ion, we chose the same element (Nd) in both OIC and EC phases in order to reduce the element diffusion between the two phases; 30 (iv) the concentration of the highly EC component NSFO in the dual phase materials was chosen to be 40 wt% in order to guarantee a continuous electron transport in a percolation network.…”

Strain induced ionic conductivity enhancement in epitaxial Ce0.9Gd0.1O2−δ thin films

“…23 However, higher activation energy values for strained films clearly indicate an expected increase in migration and association enthalpies related to oxygen vacancy diffusion for the strained lattice when compared to the strain-free one. 14 In polycrystalline CGO, the grain boundary acts as blocking surface and the resistance offered to oxygen ionic conduction is larger to cross the grain boundary than to through bulk/grain interior. Minimizing the grain boundary network via depositing epitaxial films leads to reduce resistance contribution from grain boundaries which results in the ionic conductivity enhancement.…”

“…In another report, it has been shown that lattice-strain induced in polycrystalline ceria by doping it with trivalent cations (Nd 3þ and Nd þ3 /Sm 3þ as compared to Gd þ3 ) not only enhances the ionic conductivity but also changes the activation energy. [14][15][16][17] However, the information available on epitaxy and its influence on the electrical properties of CGO thin films is limited. The major difficulty in evaluating and explaining the electrical properties of CGO thin films is to separate the ionic conductivity from the total measured conductivity.…”

Effect of transition metal oxides doping on Ce0.9Sm0.05Nd0.05O1.95 solid electrolyte materials

“…Solid electrolytes are the most important and indispensable component of SOFCs that govern the performance and to a large extent the design of the system [3]. Currently, the yttria-stabilized zirconia (YSZ) is the commonly applied electrolyte for SOFCs, however, its high operating temperature (800-1000 ℃) leads to a severe criteria for other construction materials, as well as short service times [4,5].…”