Thermal, mechanical and phase stability of LaCoO3 in reducing and oxidizing environments
Abbreviated Journal Title
J. Power Sources
reduction; perovskite; thermal expansion; stability; fuel cells; MAGNETIC-PROPERTIES; SPIN TRANSITION; PEROVSKITE; OXIDES; REDUCTION; NONSTOICHIOMETRY; LA4CO3O10+DELTA; EXPANSION; ETHYLENE; Electrochemistry; Energy & Fuels
Thermal, mechanical, and phase stability of LaCoO3 perovskite in air and 4% H-2/96% 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 degrees 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 degrees 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 degrees C with a formation of the metallic Co and La2O3 at 600 degrees C. In the bulk form, LaCoO3 undergoes a series of expansion and contractions due to phase transformations beginning around 500 degrees C with very intensive chemical/phase changes at 800 degrees 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. (C) 2008 Elsevier B.V. All rights reserved.
Journal of Power Sources
"Thermal, mechanical and phase stability of LaCoO3 in reducing and oxidizing environments" (2008). Faculty Bibliography 2000s. 865.