Thermal, mechanical and phase stability of LaCoO3 in reducing and oxidizing environments

M. Radovic, S. A. Speakman, L. F. Allard, E. A. Payzant, E. Lara-Curzio, Waltraud M Kriven, J. Lloyd, L. Fegely, N. Orlovskaya

Research output: Contribution to journalArticlepeer-review

Abstract

Thermal, mechanical, and phase stability of LaCoO3 perovskite in air and 4% H2/96% Ar reducing atmosphere have been studied by thermal mechanical analysis (TMA), high temperature microhardness, and high temperature/room temperature X-ray diffraction. The thermal behavior of LaCoO3 in air exhibits a non-linear expansion in the 100-400 °C temperature range. A significant increase of coefficient of thermal expansion (CTE) measured in air both during heating and cooling experiments occurs in the 200-250 °C temperature range, corresponding to a known spin state transition. LaCoO3 is found to be highly unstable in a reducing atmosphere. In case where LaCoO3 was present as a powder, where surface reduction mechanism would prevail, the reduction starts as earlier as 375 °C with a formation of the metallic Co and La2O3 at 600 °C. In the bulk form, LaCoO3 undergoes a series of expansion and contractions due to phase transformations beginning around 500 °C with very intensive chemical/phase changes at 800 °C and above. These expansions and contractions are directly related to the formation of La3Co3O8, La2CoO4, La4Co3O10, La2O3, CoO, and other Co compounds in the reducing atmosphere. Although LaCoO3 is a good ionic and electronic conductor and catalyst, its high thermal expansion as well as structural, mechanical, and phase instability in reducing environments present a serious restriction for its application in solid oxide fuel cells, sensors or gas separation membranes.

Original languageEnglish (US)
Pages (from-to)77-83
Number of pages7
JournalJournal of Power Sources
Volume184
Issue number1
DOIs
StatePublished - Sep 15 2008

Keywords

  • Fuel cells
  • Perovskite
  • Reduction
  • Stability
  • Thermal expansion

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering

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