Electrical transport properties of aliovalent cation‐doped CeO₂

Abstract

We report the comparative electrical properties of monovalent (Na + ), divalent (Ca 2+ , Sr 2+ ), trivalent (In 3+ , La 3+ ) and coupled substitution of divalent and trivalent (Ca 2+ + Sm 3+ ) cation-doped CeO 2 . The investigated samples were prepared by solid-state reaction (ceramic) using the corresponding metal oxides and salts in the temperature range 1000-1600 • C in air. Powder X-ray diffraction (PXRD), laser particle size analysis (LPSA), scanning electron microscopy (SEM), and ac impedance spectroscopy measurements were employed for structural, morphology, and electrical characterization. PXRD studies reveal the formation of single-phase cubic fluorite-type structures for all investigated samples except those doped with In 3+ . The variation of lattice parameters is consistent with ionic radii (IR) of the dopant metal ions, with the exception of Na + -doped CeO 2 . Our attempt to substitute In 3+ for Ce 4+ in CeO 2 using both ceramic and wet chemical methods was unsuccessful. Furthermore, diffraction peaks attributed to CeO 2 and In 2 O 3 were observed up to sintering conditions of 1600 • C. Among the single-phase compounds investigated, Ce 0.85 Ca 0.05 Sm 0.1 O 1.9 exhibits the highest bulk conductivity of 1.3 × 10 −3 S/cm at 500 • C with activation energy of 0.64 eV in air. The electrical conductivity data obtained for Ce 0.85 Ca 0.05 Sm 0.1 O 1.9 in air and Ar were found to be very similar over the investigated temperature range, indicating the absence of p-electronic conduction in the high oxygen partial pressure (pO 2 ) range which is consistent with literature reported on Sm-doped CeO 2 .

Atomic-scale insights into electro-steric substitutional chemistry of cerium oxide

“…Co-substituting two cation species is a promising approach for combining the positive effects of the substitution of single cations, that is beyond a mere additive effect. [18][19][20] Fig. S3 shows the oxygen ion diffusion behavior of the Gd 3+ /Ca 2+ , Nd 3+ /Ca 2+ and Lu 3+ /Ca 2+ co-substituted systems.…”

“…Pearce and Thangadurai found that CeO 2 ceramics co-doped with rare-earth (La 3+ , Sm 3+ ) and alkaline earth ions (Ca 2+ , Sr 2+ ) exhibit higher ionic conductivities than those seen in singly-doped systems. 19 According to Xu et al, 20 the ionic conductivity of Ce 0.8+x Y 0.2-2x Ca x O 1.9 (x=0-0.1) at 700 °C initially increased and then decreased as the Ca 2+ concentration was increased further (34.2, 47.2 and 19.2 mS cm −1 for x=0, 0.05, and 0.1, respectively).…”

Structural and electrochemical characterization of Ce0.85Ca0.05Sm0.1O1.9 oxide ion electrolyte with Sr-doped LaMnO3 and SmCoO3 cathodes

“…We were able to optimize the bulk oxygen ion conductivity for Ce 0.85 Ca 0.05 Sm 0.1 O 1.9 in air (CCS) at 5.4×10 −3 S/cm at 700°C, which is comparable to that of YSZ [23]. The current study investigates the chemical compatibility of the CCS oxide ion electrolyte in air between 700 and 800°C with the IT-SOFC cathode material, SSC, and compares its electrochemical properties with that of conventional LSM cathodes.…”

Incorporation of Sb5+into CeO2: local structural distortion of the fluorite structure from a pentavalent substituent

“…In fact ceria is remarkably accommodating in terms of the substituent species that can be taken up and elements from all parts of the Periodic Table have been reported as substituting for cerium in its structure. 15 This includes transition-metals such as Fe 16 and Ti 17 , s-block cations, such as Ca 18 and Na 19 and main-group elements such as In 20 and Pb. 21 Each substituent element brings its own coordination preference and distinctive chemistry to the material that may be beneficial for catalytic applications.…”