Predictions and correlation analyses of Ellingham diagrams in binary oxides

Kavli Affiliate: Darrell G. Schlom

| First 5 Authors: Shun-Li Shang, Shuang Lin, Michael C. Gao, Darrell G. Schlom, Zi-Kui Liu

| Summary:

Knowing oxide-forming ability is vital to gain desired or avoid deleterious
oxides formation through tuning oxidizing environment and materials chemistry.
Here, we have conducted a comprehensive thermodynamic analysis of 137 binary
oxides using the presently predicted Ellingham diagrams. It is found that the
active elements to form oxides easily are the f-block elements (lanthanides and
actinides), elements in the groups II, III, and IV (alkaline earth, Sc, Y, Ti,
Zr, and Hf), and Al and Li; while the noble elements with their oxides
nonstable and easily reduced are coinage metals (Cu, Ag, and especially Au),
Pt-group elements, and Hg and Se. Machine learning based sequential feature
selection indicates that oxide-forming ability can be represented by electronic
structures of pure elements, for example, their d- and s-valence electrons,
Mendeleev numbers, and the groups, making the periodic table a useful tool to
tailor oxide-forming ability. The other key elemental features to correlate
oxide-forming ability are thermochemical properties such as melting points and
standard entropy at 298 K of pure elements. It further shows that the present
Ellingham diagrams enable qualitatively understanding and even predicting
oxides formed in multicomponent materials, such as the Fe-20Cr-20Ni alloy (in
wt.%) and the equimolar high entropy alloy of AlCoCrFeNi, which are in
accordance with thermodynamic calculations using the CALPHAD approach and
experimental observations in the literature.

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