Title

Thermal, Mechanical And Phase Stability Of Lacoo3 In Reducing And Oxidizing Environments

Keywords

Fuel cells; Perovskite; Reduction; Stability; Thermal expansion

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. © 2008 Elsevier B.V.

Publication Date

9-15-2008

Publication Title

Journal of Power Sources

Volume

184

Issue

1

Number of Pages

77-83

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.jpowsour.2008.05.063

Socpus ID

48149096059 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/48149096059

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