Energetics of dysprosia-stabilized bismuth oxide electrolytes

Tien B. Tran, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

With ionic conductivities superior to conventional doped zirconia and ceria at intermediate temperatures (IT, 700-800 °C), bismuth oxide (BiO 1.5) materials based on the defect fluorite structure are promising electrolyte candidates for solid oxide fuel cells (SOFCs) operating at reduced temperatures. In order to investigate the energetics of stabilized BiO 1.5 in the fluorite structure, DyO 1.5-stabilized BiO 1.5 (DSB) over a range of compositions was synthesized by solid state reaction and quenched. Using high temperature oxide melt solution calorimetry in molten 3Na 2O·4MoO 3 at 702 °C, enthalpies of formation at 25 °C were determined. Relative to the phases of the oxide end-members stable at room temperature (monoclinic BiO 1.5 and C-type DyO 1.5), the formation of Bi 1-xDy xO 1.5 is endothermic at x < 0.30 and becomes slightly exothermic toward the upper phase boundary (x = 0.50). These data suggest that this system is slightly stabilized, and there is only a moderate (1-2 orders of magnitude) decrease in the volatility and susceptibility to reduction of bismuth oxide at high temperatures. However, high conductivity still makes the system potentially useful at 700 °C and below. Similar to findings for rare earth-doped zirconia, hafnia, and ceria, a negative interaction parameter for mixing in the solid solution suggests a tendency for short-range ordering, and the increasingly exothermic ΔH mix with increasing x parallels the conductivity decrease with increasing dopant content.

Original languageEnglish (US)
Pages (from-to)4185-4191
Number of pages7
JournalChemistry of Materials
Volume24
Issue number21
DOIs
StatePublished - Nov 13 2012
Externally publishedYes

Keywords

  • bismuth oxide
  • fluorite
  • solid oxide fuel cells
  • thermodynamics

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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