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Page 4 of 15 Wang et al. J Mater Inf 2023;3:3 https://dx.doi.org/10.20517/jmi.2022.45

used for imaging, and a selected area diffraction (SAD) aperture of 40 µm was used for diffraction; in
diffraction mode, the camera length was 1.1 m TEM images and diffraction patterns were acquired and
analyzed using Thermo Fisher TIA software.

Scanning-TEM (STEM) images and STEM-EDS elemental maps were obtained for each FIB-prepared TEM
sample using a Thermo Fisher Titan Themis TEM operating at 300 keV, gun lens = 3, spot size = 3,
CLA(2) = 70 µm, camera length = 130 mm, and beam current: ca. 1.0 nA, and equipped with a Thermo
Fisher Super-X Si drift detector (SSD) x-ray spectrometer (ca. 25-35 kcps during STEM-EDS map
acquisition on the sample). STEM-EDS spectra and elemental maps were acquired and analyzed using
Thermo Fisher Velox software, with input parameters set as: sample thickness: 100 nm, density correction:
3
6.0 g/cm , Brown-Powel Ionization cross-section model, 1 sigma Gaussian blur for pre-filter and for post-
filter.

COMPUTATIONAL PROCEDURE
The CALPHAD approach is considered the computational tool in the present study, which is highly
dependent on the reliability of the thermodynamic databases that are usually assessed and constructed using
existing literature data. With the corresponding database ready, thermodynamic simulations can thus be
conducted using the minimization of the Gibbs free energy of the current system in the Thermo-Calc
software. So far, the CALPHAD approach has already been considered and utilized extensively and proven
to be a significantly effective tool in the field of SOFCs [13-16,20-24] .

To perform the simulations in the current LSCF system, the thermodynamic database established by
Zhang has been employed in the present work, where detailed thermodynamic parameters can be found.
[25]
Based on the compound energy formalism, the LSCF perovskite phase is modeled with three sublattices:

3+
2+
4+
3+
2+
2+
Perovskite: (La , Sr , Va) (Co , Co , Co , Fe , Fe , Fe , Va) (O , Va) 3
2-
3+
4+
1
1
where Va stands for Vacancy. There are, in total, 42 end-members in this perovskite phase, such as (La ) 1
3+
2-
3+
(Fe ) (O ) , where most of them are not charge neutral. The charge neutrality will be considered and
3
1
maintained when doing simulations in Thermo-calc. Thus, the Gibbs energy per mole molecule can be
described via the CALPHAD formalism:
where y, y, and y represent the site fraction of each species in A-, B-, and oxygen-site, respectively. is
k
j
i
the molar Gibbs energy of the end-members in the system, while is the excess Gibbs energy taking
into account the interaction parameters among the sublattices. Meanwhile, several oxide solution phases are
predicted to form during the simulations, of which the Co/Fe-containing Halite and Spinel phases, as the
most important secondary phases, are described as:
2+
3+
2-
Halite: (Co , Fe , Fe , Va) (O ) 1
2+
1
Spinel: (Co , Co , Fe , Fe ) (Co , Co , Fe , Fe , Va) (O ) 4
3+
2+
2+
2-
3+
3+
2+
3+
2+
1
2