Terbium gallium garnet (Tb3Ga5O12, TGG) has a high Verdet constant, excellent optical performance, high thermal conductivity and laser damage threshold in the visible and near-infrared bands. The above advantages make TGG an important magnetic for optical isolator Light material. TGG single crystal will produce gallium oxide volatilization during the preparation process and affect its crystal quality, and it is difficult to obtain large-size single crystal. In comparison, TGG ceramics can achieve transparency at a lower sintering temperature and diversified sintering mechanisms, which can effectively avoid many problems such as gallium oxide volatilization in crystal growth, thereby obtaining high-quality magneto-optic ceramics. In addition, ceramics have the advantages of easy preparation of large-sized materials, high fracture toughness, and short preparation cycle. Therefore, TGG magneto-optical ceramics have good application prospects.
Related research progress
Recently, the research group of transparent and optical functional ceramics led by Li Jiang, a researcher of Shanghai Institute of Ceramics, Chinese Academy of Sciences, has made progress in the research of terbium gallium garnet based magneto-optical ceramics. The team used 1.0at% Ce: TGG nano-powder synthesized by co-precipitation method as raw materials, combined with air sintering and hot isostatic pressing post-treatment (HIP) technology to prepare Ce: TGG ceramics with excellent performance. The linear transmittance of the ceramic at 1064 nm reached 81.7%, and the Verdet constant at 632.8 nm reached -143.4 rad · T-1 · m-1, which was 5% higher than the commercial TGG crystal.
At present, only TGG magneto-optical ceramics prepared by the Japanese God Island Chemical Company can meet the application requirements of optical isolators for high-power lasers, but the preparation details are not yet clear, and it is urgent to break the technical barriers. In recent years, the team of researcher Li Jiang has cooperated with Professor Liu Qiang of the School of Materials Science and Technology of Jiangsu University to carry out research work on TGG magneto-optic ceramics, and has achieved a series of research results. The team independently synthesized high-quality TGG nano-powders, and adjusted the composition, morphology and agglomeration state of the powders by optimizing the synthesis process (Opt. Mater., 2019, 90: 26-32; J. Inorg. Mater., 2019, 34 (7): 791-796). The optimized TGG powder is pure cubic phase, and has good dispersibility and sintering activity, suitable for the subsequent sintering of TGG magneto-optical ceramics. Considering the evaporation of gallium oxide, the team used a two-step sintering method to prepare TGG transparent ceramics with excellent optical quality and magneto-optical properties. The linear transmittance of the TGG ceramic at 1064 nm reached 80.3% (close to its theoretical transmittance), and exhibited magneto-optical comparable to single crystal (-134 rad · T-1 · m-1) Performance, its Verdet constant at 632.8 nm is about -136 rad · T-1 · m-1. Relevant research results were published in the international journal Optical Material (Opt. Mater., 2019, 62: 205-21). At the same time, this is the first report in China of high-performance TGG magneto-optical ceramics prepared with self-synthesized TGG powder as raw material .