In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides
In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides
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DOI：
10.1021/acs.chemmater.2c03088
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发表时间：
2023-01
影响因子：
8.6
通讯作者：
Matheus Pianassola;Kaden L. Anderson;Can Agca;C. Benmore;J. Mcmurray;J. Neuefeind;Charles Melcher;M. Zhuravleva
中科院分区：
文献类型：
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作者：
Matheus Pianassola;Kaden L. Anderson;Can Agca;C. Benmore;J. Mcmurray;J. Neuefeind;Charles Melcher;M. Zhuravleva
含有五种等摩尔量阳离子的高熵稀土（RE）倍半氧化物（RE2O3）已被研究用于各种应用，但对其多晶型行为和热膨胀系数知之甚少。在这里，我们评估了平均离子半径 (AIR) 对高熵 RE2O3 多晶型的影响。通过湿化学方法合成了成分 1 (Lu,Y,Ho,Nd,La)2O3(AIR = 0.938 Å) 和 2 (Gd,Eu,Sm,Nd,La)2O3(AIR = 0.982 Å) 的粉末样品，并通过在铜炉中熔化粉末来制备用于气动悬浮的珠子样品。通过空气动力学悬浮样品的原位 X 射线衍射监测从熔体冷却到 1000 °C 时的结构转变。成分1的相演化为液体、六方H型和单斜B型，成分2为液体、立方X型、H型和B型。基于它们的AIR，高熵RE2O3的总体多晶型转变遵循单稀土RE2O3的趋势，但转变温度与单稀土RE2O3不同。组合物1和2的B型相的热膨胀系数值与Gd2O3和之前公开的高熵RE2O3的热膨胀系数值相似。
High-entropy rare-earth (RE) sesquioxides (RE2O3) containing five cations in equimolar amounts have been investigated for a variety of applications, but little is known about their polymorphic behavior and coefficient of thermal expansion. Here, we evaluate the effect of the average ionic radius (AIR) on the polymorphism of high-entropy RE2O3. Powder samples of compositions 1 (Lu,Y,Ho,Nd,La)2O3(AIR = 0.938 Å) and 2 (Gd,Eu,Sm,Nd,La)2O3(AIR = 0.982 Å) were synthesized via a wet chemical method, and bead samples were prepared for aerodynamic levitation by melting the powders in a copper hearth. Structural transitions were monitored upon cooling from the melt to 1000 °C via in situ X-ray diffraction on aerodynamically levitated samples. The phase evolution was liquid, hexagonal H-type, and monoclinic B-type for composition 1 and liquid, cubic X-type, H-type, and B-type for composition 2. Based on their AIR, the general polymorphic transformations of the high-entropy RE2O3follow the trend of single-RE RE2O3, but the transition temperatures differ from those of single-RE RE2O3. The coefficient of thermal expansion values of the B-type phase of compositions 1 and 2 are similar to those of Gd2O3and previously published high-entropy RE2O3.