The Microstructure and Electronic Properties of Yttrium Oxide Doped With Cerium: A Theoretical Insight
The Microstructure and Electronic Properties of Yttrium Oxide Doped With Cerium: A Theoretical Insight
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掺铈氧化钇的微观结构和电子性能：理论见解
DOI：
10.3389/fchem.2020.00338
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发表时间：
2020
影响因子：
5.5
通讯作者：
Chen Yunhong
中科院分区：
文献类型：
--
作者：
Ju Meng;Wang Jingjing;Huang Jing;Zhang Chuanzhao;Jin Yuanyuan;Sun Weiguo;Li Shichang;Chen Yunhong
三价铈（Ce3+）掺杂氧化钇（Y2O3）主体晶体由于其流行的光学5d-4f跃迁而引起了相当大的兴趣。Y2O3:Ce体系具有优异的光学性能，但其微观结构尚不清楚。Y2O3:Ce微结构的缺乏可能成为进一步开发其潜在应用的一个问题。在此意义上，我们基于CALYPSO结构搜索方法结合密度泛函理论计算，全面研究了Y2O3:Ce晶体的结构演变。我们的结果揭示了一个新的具有R-3基团对称的Y2O3:Ce的菱形相。在主体晶体中，中心位置的Y3+离子可以被掺杂的Ce3+自然取代，形成完美的笼状结构。我们发现了一个有趣的相变，即当杂质Ce3+掺杂到主体晶体中时，Y2O3的晶体对称性从立方体变为菱形体。当Ce3+的标称浓度为3.125%时，由于主体晶体中的占位点不同，也鉴定出许多亚稳结构。模拟了Y2O3:Ce的x射线衍射图，理论结果与实验数据相吻合，证明了最低能结构的有效性。声子色散的结果表明基态结构是动态稳定的。电子性能分析表明，Y2O3:Ce具有4.20 eV的带隙，表明杂质Ce3+离子掺入Y2O3主体晶体导致绝缘体向半导体转变。同时，电子局域函数证明了晶体中O原子的强共价键可能对基态结构的稳定性有很大贡献。这些结果阐明了Y2O3:Ce的结构和键合特性，也为理解实验现象提供了有用的见解。
Trivalent Cerium (Ce3+) doped Yttrium Oxide (Y2O3) host crystal has drawn considerable interest due to its popular optical 5d-4f transition. The outstanding optical properties of Y2O3:Ce system have been demonstrated by previous studies but the microstructures still remain unclear. The lacks of Y2O3:Ce microstructures could constitute a problem to further exploit its potential applications. In this sense, we have comprehensively investigated the structural evolutions of Y2O3:Ce crystals based on the CALYPSO structure search method in conjunction with density functional theory calculations. Our result uncovers a new rhombohedral phase of Y2O3:Ce with R-3 group symmetry. In the host crystal, the Y3+ ion at central site can be naturally replaced by the doped Ce3+, resulting in a perfect cage-like configuration. We find an interesting phase transition that the crystallographic symmetry of Y2O3 changes from cubic to rhombohedral when the impurity Ce3+ is doped into the host crystal. With the nominal concentration of Ce3+ at 3.125%, many metastable structures are also identified due to the different occupying points in the host crystal. The X-ray diffraction patterns of Y2O3:Ce are simulated and the theoretical result is comparable to experimental data, thus demonstrating the validity of the lowest energy structure. The result of phonon dispersions shows that the ground state structure is dynamically stable. The analysis of electronic properties indicate that the Y2O3:Ce possesses a band gap of 4.20 eV which suggests that the incorporation of impurity Ce3+ ion into Y2O3 host crystal leads to an insulator to semiconductor transition. Meanwhile, the strong covalent bonds of O atoms in the crystal, which may greatly contribute to the stability of ground state structure, are evidenced by electron localization function. These obtained results elucidate the structural and bonding characters of Y2O3:Ce and could also provide useful insights for understanding the experimental phenomena.