Structure, Conductivity, and Thermal Expansion Studies of Redox Stable Rutile Niobium Chromium Titanates in Oxidizing and Reducing Conditions

Anna Lashtabeg*, Jesus Canales-Vazquez, John T. S. Irvine, John L. Bradley

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Materials from the solid solution with general formula Ti(1-2x)Cr(x)Nb(x)O(2) (0 20 S cm(-1) in 5% H(2)/Ar. The lowest conductivity was observed for samples low in titanium content, indicating that the reduction of Ti(4+) to Ti(3+) is primarily responsible for the high electronic conductivity in these materials. All samples showed very slow reduction kinetics, and true equilibrium was not achieved even after > 50 h in flowing 5% H(2)/Ar at 900 degrees C, suggesting that the equilibrium conductivity of these materials at 10(-20) atm may be significantly higher. Conductivity studies as a function of p(O(2)) showed complex redox behavior with indications of a number of step transitions and very slow redox kinetics. The thermal expansion coefficient was in the range of 5.6 x 10(-6) - 8.6 x 10(-6) K(-1), which changed little between reduced and fully oxidized samples.

Original languageEnglish
Pages (from-to)3549-3561
Number of pages13
JournalChemistry of Materials
Volume21
Issue number15
DOIs
Publication statusPublished - 11 Aug 2009

Keywords

  • CHARGE-TRANSPORT
  • DOPED TITANIUM-DIOXIDE
  • THERMOELECTRIC-POWER
  • DEFECT CHEMISTRY
  • HIGH-TEMPERATURE
  • CHEMICAL DIFFUSION
  • TIO2 SINGLE-CRYSTAL
  • OXIDE FUEL-CELLS
  • EQUILIBRATION KINETICS
  • ELECTRICAL-PROPERTIES

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