Grain-bulk versus grain-boundary sensitivities to redox reaction in yttria-doped ceria ceramics viewed from impedance spectroscopy

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2007-11, Vol.89 (2), p.509-515
• Main Authors: PEKO, J.-C. M, DE SOUZA, M. F, DA SILVA, C. L, DE SOUZA, D. P. F
• Format: Article
• Language: English
• Subjects: Applied physics; Argon; Ceramics; Cerium oxides; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Diffusion in solids; Electrical properties; Electronic transport in condensed matter; Exact sciences and technology; Grain boundaries; Impedance spectroscopy; Materials science; Mixed conductivity and conductivity transitions; Oxidation; Physics; Redox reactions; Self-diffusion and ionic conduction in nonmetals; Spectrum analysis; Transport properties of condensed matter (nonelectronic); Yttrium oxide
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-007-4096-4

Yttria-doped ceria ceramics were prepared and reduced in an oxygen-deficient (argon) ambient. Electrical characterization through impedance spectroscopy revealed ionic-type conduction processes in as-sintered samples, with grain–bulk and grain–boundary activation energies (H) of about 1.00 eV and 1.05 eV, respectively. Electrical results from the reduced materials showed a predominant electronic-type, relatively high conductivity for the grains (H=0.52 eV), in contrast to a still ionic-like, relatively poor conductivity for the grain boundaries (H=0.95 eV). With the support of the results processed after re-oxidizing the materials in air combined with information from literature, this apparently contradictory behavior is discussed in terms of electron trapping at (Ce3+:)-type defect complexes. The overall work strongly supports the idea that surfaces (e.g., grain boundaries) in polycrystalline ceria are indeed much more sensitive to redox interactions than lattice.