Enhanced Ionic Conductivity in Ce_0.8Sm_0.2O_1.9: Unique Effect of Calcium Co‐doping

Abstract

In order to identify new oxide ion‐conducting materials in the ceria family of oxides, the unique effect of co‐doping is explored and a novel series of Ce0.8Sm0.2–xCaxO2–δ compositions is identified that have enhanced properties compared to the single‐doped Ce0.8Sm0.2O1.9 and Ce0.8Ca0.2O1.9 compositions. Moreover, the superior characteristics of the co‐doped Ce0.8Sm0.2–xCaxO2–δ powders prepared by the mixed‐fuel process aid in obtaining 98 % dense ceramics upon sintering at 1200 °C for 6 h. Though a linear increase in conductivity is observed by replacing Sm with Ca, the composition with the maximum amount of Ca and the minimum amount of Sm exhibits a significant improvement in properties compared to the rest in the series. The composition Ce0.80Sm0.05Ca0.15O2–δ exhibits a conductivity as high as 1.22 × 10–1 S cm–1 at 700 °C with minimum activation energy (0.56 eV) and a superior chemical stability to reduction compared to any of the hitherto known (CaSm) compositions. The absence of CeIII, confirmed both from X‐ray photoelectron spectroscopy and X‐ray absorption spectroscopy, strongly suggests that the observed increase in conductivity is solely due to the oxide ion conductivity and not due to the partial electronic contribution arising from the presence of CeIII and CeIV. To conclude, the experimental results on the Ce0.8Sm0.2–xCaxO2–δ series underscore the unique effect of calcium co‐doping in identifying a cost‐effective new composition, with a remarkably high conductivity and enhanced chemical stability to reduction, for technological applications.

Low temperature fabrication of dense gadolinia-doped ceria electrolyte with enhanced electrical conductivity

“…The calculated electrical conductivity activation energies in different operating temperature regions for all of the samples prepared under different conditions are listed in Table 1. The conductivity activation energies respectively for low and high operating temperature regions are highly comparable with the previous data reported by Zhou et al [34], Steele [35] and Banerjee et al [36]. For Ce 0.9 Gd 0.1 O 1.95 , Zhou [34] reported complex association energy of 0.12 eV, and Steele [35] observed ∆H a to be 0.13 eV.…”

Fabrication and characterization of composite YSZ-La9.33Si6O26 oxygen-ion conductor

“…Generally, the Nyquist plots of an oxygen-ion conductor exhibit three parts: the arc at high frequency range is attributed to bulk effect, the one at intermediate frequency comes from the grain boundary effect, and the low-frequency part relates to electrode behavior. With increasing temperature, the arcs corresponding to grain and grain boundary effect tend to be smaller and even disappear, and only the electrode contribution can be detected at higher temperatures [15]. Figure 4 shows the complex impedance spectra of the samples, YSZ, LSO and YSZ-LSO, measured at 400 °C, 500 °C and 600 °C, respectively.…”

Synthesis, Structural and Optical Properties of Mn-Doped Ceria Nanoparticles: A Promising Catalytic Material

“…It is well known that the catalytic properties significantly improve after substitution of transition-metal ions into ceria lattice, because it depends on the type of dopant ion, dopant concentration, oxygen vacancy concentration and defect association enthalpy [2]. So that, these dopant ions greatly enhanced the number of oxygen vacancies owing to their charge compensation within lattice [2,[6][7][8]. These free oxygen vacancies within lattice were responsible to amplification catalytic properties of the nanomaterials [2,7].…”

“…So that, these dopant ions greatly enhanced the number of oxygen vacancies owing to their charge compensation within lattice [2,[6][7][8]. These free oxygen vacancies within lattice were responsible to amplification catalytic properties of the nanomaterials [2,7].…”