Surface Segregation Across Ternary Alloy Composition Space: CuxAuyPd1–x–y,The Journal of Physical Chemistry C

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Surface Segregation Across Ternary Alloy Composition Space: CuxAuyPd1–x–y
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-04-17 , DOI: 10.1021/acs.jpcc.0c02058
Chunrong Yin ₁ , Zhitao Guo ₁ , Andrew J. Gellman _{1,

2}

Affiliation

Surface segregation is a phenomenon common to all multicomponent materials and one that plays a critical role in determining their surface properties. Comprehensive studies of surface segregation versus bulk composition in ternary alloys have been prohibitive because of the need to study many different compositions. In this work, high-throughput low-energy He⁺ ion-scattering spectra and energy-dispersive X-ray spectra were collected from a Cu_xAu_yPd_1–x–y composition spread alloy film under ultrahigh vacuum conditions. These have been used to quantify surface segregation across the entire Cu_xAu_yPd_1–x–y composition space (x = 0 → 1 and y = 0 → 1 – x). Surface compositions at 164 different bulk compositions were measured at 500 and 600 K. At both temperatures, Au shows the greatest tendency for segregation to the top-most surface while Pd is always depleted from the surface. Higher temperatures enhance the Au segregation. Segregation at most of the binary alloy bulk compositions matches with observations previously reported in the literature. However, surface compositions in the CuPd B2 composition region reveal segregation profiles that are nonmonotonic in bulk alloy composition. These were not observable in prior studies because of their limited resolution of composition space. An extended Langmuir–MacLean model, which describes ternary alloy segregation, has been used to analyze experimental data from the ternary alloys and to estimate pair-wise segregation free energies and segregation equilibrium constants. The ability to study surface segregation across the ternary alloy composition space with high-throughput methods has been validated, and the impact of bulk alloy phase on surface segregation is demonstrated and discussed.

中文翻译：

三元合金组成空间中的表面偏析：Cu _x Au _y Pd _{1– x – y}

表面偏析是所有多组分材料常见的现象，并且在确定其表面性能方面起着至关重要的作用。由于需要研究许多不同的组成，因此对三元合金中表面偏析与整体组成的综合研究一直是令人望而却步的。在这项工作中，在超高真空条件下从Cu _x Au _y Pd _1–_x_–_y成分扩散合金膜中收集了高通量低能量He ⁺离子散射光谱和能量色散X射线光谱。这些已被用于量化整个Cu _x Au _y Pd _1–_x_–_y合成空间（ x = 0→1和y = 0→1 – x）。在500和600 K下测量了164种不同的本体组成下的表面组成。在两种温度下，Au都表现出最大的偏析到最顶部表面的趋势，而Pd总是从表面耗尽。较高的温度会增强Au的偏析。大多数二元合金块状成分的偏析与文献中先前报道的观察结果相符。但是，CuPd B2组成区域中的表面组成显示出在整体合金组成中非单调的偏析轮廓。由于组成空间的分辨率有限，这些在以前的研究中无法观察到。扩展的Langmuir–MacLean模型描述了三元合金的偏析，已用于分析三元合金的实验数据，并估计成对的偏析自由能和偏析平衡常数。验证了通过高通量方法研究三元合金组成空间中表面偏析的能力，并论证并讨论了整体合金相对表面偏析的影响。

更新日期：2020-04-17

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