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@PHDTHESIS{Huang:14775,
author = {Huang, Bingxin},
title = {{T}hermo-{M}echanical {P}roperties of {M}ixed
{I}on-{E}lectron {C}onducting {M}embrane {M}aterials},
volume = {124},
issn = {1866-1793},
school = {RWTH Aachen},
type = {Dr. (Univ.)},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-14775},
isbn = {978-3-89336-746-7},
series = {Schriften des Forschungszentrums Jülich : Energie $\&$
Umwelt / Energy $\&$ Environment},
pages = {130 S.},
year = {2010},
note = {Record converted from VDB: 12.11.2012; RWTH Aachen, Diss.,
2010},
abstract = {The thesis presents thermo-mechanical properties of
La$_{0.58}$Sr$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-\delta}$
(LSCF) and
Ba$_{0.5}$Sr$_{0.5}$Co$_{0.8}$Fe$_{0.2}$O$_{3-\delta}$
(BSCF) perovskite materials, which are considered as oxygen
transport membranes (OTM) for gas separation units.
Ring-on-ring bending test with disk-shaped samples and
depth-sensitive micro-indentation have been used as
macroscopic and microscopic tests, respectively. In
addition, the thermo-mechanical properties of a third OTM
candidate material La$_{2}$NiO$_{4+\delta}$(LNO) were
investigated. The results of the thermo-mechanical
measurements with the BSCF revealed an anomaly between 200
°C and 400 °C. In particular, the temperature dependence
of Young’s modulus shows a minimum at ~ 200 °C. Fracture
stress and toughness exhibit a qualitatively similar
behavior with a minimum between 200 °C and 400 °C, before
recovering between 500 °C and 800 °C. X-ray diffraction
analyses verified that BSCF remains cubic in the relevant
temperature range. Hence the anomalies were assumed to be
related to the transition of Co$^{3+}$ spin states reported
for other Co-containing perovskites. This assumption could
be experimentally confirmed by magnetic susceptibility
measurements. The fracture surfaces of the specimens are not
affected by the mechanical anomalies at intermediate
temperatures, since only a transgranular fracture mode has
been observed. Complementary to the mechanical
characterization of BSCF, also the temperature dependency of
fracture stress and elastic behavior of LSCF have been
determined. Phase compositions of LSCF have been studied by
in-situ high temperature XRD. Changes in phase composition
with temperature are observed. At ambient temperature the
LSCF perovskite material comprises two phases: rhombohedral
and cubic symmetry. The ratio of the two phases depends on
both cooling rate and atmosphere. The transition of
rhombohedral to cubic occurs between 700 °C and 800 °C in
air. The transition appears to be associated with a change
of heat capacity. The [...]},
cin = {IEK-2},
cid = {I:(DE-Juel1)IEK-2-20101013},
pnm = {Rationelle Energieumwandlung},
pid = {G:(DE-Juel1)FUEK402},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/14775},
}