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

41 Citations (Scopus)

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 - 2015

Fingerprint

Cerium compounds
Grain boundaries
grain boundaries
electrical resistivity
conductivity
Chemical analysis
Electron energy loss spectroscopy
spectroscopy
Electrolytes
Electron microscopes
electron microscopes
energy dissipation
electrolytes
electron energy
Scanning
Spray drying
scanning
mixed oxides
Oxygen vacancies
Oxides

Keywords

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

ASJC Scopus subject areas

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

Cite this

Electrical conductivity and grain boundary composition of Gd-doped and Gd/Pr co-doped ceria. / Bowman, William J.; Zhu, Jiangtao; Sharma, Renu; Crozier, Peter.

In: Solid State Ionics, Vol. 272, 2015, p. 9-17.

Research output: Contribution to journalArticle

Bowman, William J. ; Zhu, Jiangtao ; Sharma, Renu ; Crozier, Peter. / Electrical conductivity and grain boundary composition of Gd-doped and Gd/Pr co-doped ceria. In: Solid State Ionics. 2015 ; Vol. 272. pp. 9-17.
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N2 - 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.

AB - 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.

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