Electrical conductivity and grain boundary composition of Gd-doped and Gd/Pr co-doped ceria

William J. Bowman, Jiangtao Zhu, Renu Sharma, Peter Crozier

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

We characterize electrical conductivity, microstructure, nano-scale grain boundary structure and chemistry of ceria electrolytes with nominal compositions of Gd0.2Ce0.8O2-δ (GDC) and Gd0.11Pr0.04Ce0.85O2-δ (GPDC). The electrolytes are fabricated using mixed oxide nanopowders synthesized by spray drying. AC impedance spectroscopy was performed from 150 °C to 700 °C in air to determine grain-interior electrical conductivity. Grain-boundary conductivity was determined below 300 °C. The grain-interior conductivity of the GPDC was higher than that of GDC by as much as 10 times, depending on the temperature. The GPDC specific grain-boundary conductivity was measured to be approximately 100 times higher than that of GDC. Energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) confirmed the grain-to-grain compositional uniformity of both materials following heat treatments. Grain boundaries were free of glassy intergranular phases; dopant concentration and Ce oxidation state were found to vary significantly near grain boundaries. Boundary core composition was estimated from STEM EELS to be Gd0.62Ce0.38O2-δ, and Gd0.29Pr0.16Ce0.55O2-δ in GDC and GPDC, respectively. Pr segregation to grain boundaries in the GPDC is hypothesized to enhance conductivity by both decreasing oxygen vacancy migration energy, and inducing mixed ionic-electronic conductivity in the near-boundary region.

Original languageEnglish (US)
Pages (from-to)9-17
Number of pages9
JournalSolid State Ionics
Volume272
DOIs
StatePublished - Apr 2015

Keywords

  • Doped ceria
  • Electron energy-loss spectroscopy
  • Grain boundary
  • Impedance spectroscopy
  • Scanning transmission electron microscopy
  • Spray drying

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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