Crystal growth and phase formation of high‐entropy rare‐earth monoclinic aluminates
Crystal growth and phase formation of high‐entropy rare‐earth monoclinic aluminates
复制标题
高熵稀土单斜铝酸盐的晶体生长和相形成
DOI：
10.1111/jace.19320
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发表时间：
2023
影响因子：
3.9
通讯作者：
Zhuravleva, Mariya
中科院分区：
文献类型：
--
作者：
Pianassola, Matheus;Loveday, Madeline;Lalk, Rebecca;Pestovich, Kimberly;Melcher, Charles L.;Zhuravleva, Mariya
首次使用微下拉法通过定向凝固生长高熵稀土单斜铝酸盐晶体。用通式 RE4Al2O9 配制了五种高熵组合物，其中 RE 是五种稀土元素的等原子混合物。稀土元素包括Lu、Yb、Er、Y、Ho、Dy、Tb、Gd、Eu、Sm、Nd和La。高温粉末X射线衍射和Rietveld结构细化表明所有晶体都是单一单斜相，稀土平均离子半径不影响相纯度。在室温下，细化的晶格参数随着五种组合物平均离子半径的增加而一致增加。其中一种晶体在 1100-1150°C 范围内具有典型的单稀土 RE4Al2O9 高温相变，其中包括加热时晶格收缩。差示扫描量热法表明了与该相变相对应的热事件。电子探针微量分析显示晶体表面存在富铝夹杂物。含 Tb 的晶体具有深色表面特征，在还原气氛中退火后颜色变浅，这表明 Tb4+ 可能是造成深色特征的原因。
For the first time, high‐entropy rare‐earth monoclinic aluminate crystals were grown via directional solidification using the micro‐pulling‐down method. Five high‐entropy compositions were formulated with a general formula RE4Al2O9, where RE is an equiatomic mixture of five rare‐earth elements. The rare‐earth elements included were Lu, Yb, Er, Y, Ho, Dy, Tb, Gd, Eu, Sm, Nd, and La. High‐temperature powder X‐ray diffraction and Rietveld structure refinement indicated that all crystals were a single monoclinic phase and that rare‐earth average ionic radius did not affect phase purity. At room temperature, the refined lattice parameters increased consistently with increasing average ionic radii of the five compositions. One of the crystals had a typical high‐temperature phase transition of single‐RE RE4Al2O9in the range of 1100–1150°C, which consisted of a lattice contraction upon heating. Differential scanning calorimetry indicated a thermal event corresponding to that phase transition. Electron probe microanalysis revealed Al‐rich inclusions on the surface of the crystals. Crystals containing Tb had dark surface features that became lighter after annealing in a reducing atmosphere, which indicated that Tb4+may be responsible for the dark features.