高含铈稀土铁石榴石晶体的结构设计、EFG-LPE法晶体生长及磁光性能研究

Magneto-optical crystals are the indispensable key functional materials for the new generation of fiber-optic communication, internet of things and smart power grids. The cerium iron garnet crystal with high Ce3+ concentration is expected to have the strong magneto-optical effect, which makes it become the ideal material for the high performance magneto-optical device with a good application prospect. However, the cerium iron garnet single crystal cannot be obtained until now because it is thermodynamically unstable. Therefore, this project plans to make two-pronged efforts on the crystal structure design and the innovation of crystal growth method. Firstly, based on the garnet structure and combined with the crystal engineering and the quantum theoretical calculation, the rare-earth iron garnet compounds with high Ce3+ concentration that have the room-temperature thermodynamic stability and have the excellent magneto-optical properties will be searched. Secondly, a new crystal growth method of EFG-LPE, improved form EFG method, will be used to grow the high-quality single crystal with uniform ion distribution. On these bases, the mechanisms of crystal growth and defect formation will be studied, and the influences of doping ions on the magnetic and magneto-optical properties will be discussed. By these research efforts, new crystal materials with strong magneto-optical effect are expected be obtained, a new crystal growth method will be developed, and the magneto-optical effect mechanism and structure-performance relationship will be revealed. These will undoubtedly have the important academic significance and the practical application value. The research on structure design, crystal growth method and structure-performance relationship also provide the beneficial references for exploring other new crystal materials.

磁光晶体是新一代光纤通讯、物联网、智能电网中不可或缺的关键功能材料。含高浓度Ce3+的铈铁石榴石晶体预期具有极强磁光效应，是制作新一代高性能磁光器件的理想材料，有很好的应用前景。然而，铈铁石榴石存在热力学不稳定、无法制成单晶的问题。本项目拟从晶体结构设计和生长方法创新两方面入手给予解决。首先，基于石榴石结构，结合晶体工程学和量子理论计算，探寻室温热力学稳定、磁光性能优异的高含Ce3+稀土铁石榴石化合物；其次，改进导模提拉法，采用导模提拉-液相外延法生长离子分布均匀的高质量单晶。在此基础上，研究晶体生长机理和缺陷产生机理，探讨离子掺杂对晶体磁性和磁光性能的影响规律。项目研究有望获得具强磁光效应的新晶体材料、开发出晶体生长新方法、揭示材料的磁光效应机理和构效关系，无疑具有重要的学术意义和实际应用价值。在晶体结构设计、生长方法、构效关系等方面的探索也可为其他新型晶体材料研究提供有益的参考与借鉴。

磁光材料是光信息产业关键的核心材料。当前我国光通信行业用的磁光晶体完全依赖进口，对我国信息产业的发展有着极大不利的影响。掺铈稀土铁石榴石晶体具有居里温度高、磁光效应强等优点，但却存在Ce3+易变价、掺杂浓度偏低、晶体生长困难的难题。.项目结合晶体工程学原理和量子理论计算，开展了CexR3-xFe5-yMyO12(M=Sc,Ga等)、Ce1-xSrxFe1-xVxO3、Ce1-xSrxAl1-xTixO3、Ce3Sc2Ga3O12等钙钛矿型、石榴石型高含铈化合物的合成、晶体生长、结构解析、磁性和磁光性能等研究，探讨这类化合物的结构演变、结构中铈离子价态和容忍浓度及磁光性能等规律。项目研究发现稀土铁石榴石结构中，十二面体和八面体格位离子半径适当增大有利于半径偏大的Ce3+、Bi3+离子掺入，从而大幅提升磁光效应。此外，还发现铈离子所处的化学环境对其价态影响很大。化合物中与铈离子相邻的阳离子电负性越大，则越容易合成含Ce3+化合物。在此基础上，通过优化Ga3+、Sc3+、Ca2+等离子掺杂浓度，生长获得Ce3+掺杂浓度达18%、比法拉第旋转角达1534deg. cm-1@1550nm的Ce,Sc,Ca:GIG晶体，这是目前我们所知Ce3+掺杂浓度最高、比法拉第旋转角最大的Ce:RIG磁光晶体。此外，本项目还研究获得Ce1-xSrxFe1-xVxO3/Si薄膜和Ce3Sc2Ga3O12晶体两种高含铈、强磁光效应的新磁光材料。项目还在晶体生长进行创新，采用自助溶剂导模提拉法成功生长出质量较高的厘米级单晶，具有无须外延基片、生长可控性好、速度快等优点。项目研究已发表12篇论文，2项发明专利授权，获得2020年第六届中国国际“互联网+”大学生创新创业大赛金奖。