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Enhanced Shrinkage of Lanthanum Strontium Manganite (La 0.90 Sr 0.10 MnO 3+δ ) Resulting from Thermal and Oxygen Partial Pressure Cycling
Author(s) -
McCarthy Benjamin P.,
Pederson Larry R.,
Anderson Harlan U.,
Zhou XiaoDong,
Singh Prabhakar,
Coffey Gregory W.,
Thomsen Edwin C.
Publication year - 2007
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.01890.x
Subject(s) - partial pressure , isothermal process , lanthanum manganite , oxygen , lanthanum , shrinkage , temperature cycling , analytical chemistry (journal) , strontium , materials science , atmospheric temperature range , dilatometer , mineralogy , chemistry , thermodynamics , thermal , thermal expansion , inorganic chemistry , metallurgy , composite material , environmental chemistry , electrode , physics , organic chemistry , electrolyte
Exposure of (La 0.90 Sr 0.10 ) 0.98 MnO 3+δ (LSM‐10) to repeated oxygen partial pressure cycles (air/10 ppm O 2 ) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700°–1000°C were orders of magnitude higher than Makipirtti–Meng model estimations based on stepwise isothermal dilatometry results at a high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900°C. Shrinkage was the greatest when LSM‐10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria are reestablished, whereas the latter condition does not lead to excess vacancy concentrations.