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Chong et al. J Mater Inf 2023;3:21 https://dx.doi.org/10.20517/jmi.2023.17 Page 15 of 18

Figure 15. Cross-sectional morphologies and distribution of elements from EPMA EPMA mapping images Pt Al Ta after 100 h
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oxidation in air at 1,300 °C. (A) Cross-sectional morphology; (B1)-(B4) Pt, Al, O, and Ta map distribution, respectively; (C) Linear
distribution of Pt, Al, O, and Ta. EPMA: Electron probe micro-analyzer.
These results are also consistent with the EPMA mapping analysis [Figure 14], where the dark region is
Al O , and the bright region mainly contains Pt, Ta, and a small amount of O. So, we presume that the
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bright area mainly consists of Pt, PtO , and Ta O ; and Al O and AlTaO in the dark region; and Ta O
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mainly in the dark area.
Figure 15 shows the cross-section EPMA mapping of the oxidized samples, indicating that no dense oxides
on the sample surface are observed. Figure 15B shows that at the interior, both Al and Ta are found in
combination with O. According to Figure 15C, the dispersive gray areas are enriched with O and Ta, but
almost no Al, which could be identified as Ta O . The dark oxidized regions with enriched Al and O, along
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with some Ta, are observed in the interior of the alloy, indicating the formation of Al O , AlTaO , and
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Ta O . The oxidation kinetics of Pt Al Ta is similar to that of Pt Al Hf , as shown in Figure 1; even the
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weight gain is more pronounced, attributed to more intense internal oxides formed than those in the
Pt Al Hf alloy.
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