新型DAST晶体的原料制备、可控成核及其机理研究

DAST crystals are proved to be one of the most potential materials for THz generation. Up to now, there are no raw materials used for growing DAST crystals in the market, which limits the following investigation and application. Therefore, it is an urgent need to prepare high-purity raw materials of DAST crystals. The synthesis process of organic DAST raw materials is very complicated, and many factors can influence the obtaining of final product. There is no synthesis process for DAST raw materials reported in detail at home and abroad. Otherwise, spontaneous nucleation method is often used to grow DAST crystals at present, but the nucleation position and quantity are difficult to control, which will affect the size and quality of crystal growth. In order to improve the yield and purity of synthesized DAST, the applicants will research and develop an optimal synthesis and purification technology. At first, the effect factors and function mechanisms during the reaction process will be analyzed, and the proportion among the reactants as well as the ratio between the solvent and solute will be adjusted. Based on the further study on crystal nucleation and growth mechanisms, the metastable zone width can be broadened and the stability of the growth solution can be improved by optimizing the growth device and technology process. As a result, the defect of the present spontaneous nucleation pattern for DAST crystal growth will be overcome, and the controlled growth of high quality crystals will be come true. Several pieces of invention patents with independent intellectual property rights will be applied. This study has important theoretical meaning and application value for improving the synthesis process of DAST raw materials and crystals, and also has significant promotion function in the development of THz technology.

DAST晶体是具有良好发展潜力的THz辐射源材料，但市场尚无制备晶体所需的DAST原料出售，限制了后续晶体的研究和应用，因此制备高纯度DAST晶体原料已成为迫切需要。DAST属有机物，制备工艺复杂，影响因素较多，难以获得目标产物，其详细制备工艺国内外尚无报道；且目前采用的自发成核法生长晶体，成核位置和数量较难控制，限制了晶体生长。本课题通过分析各工艺参数对反应过程的影响和作用机理，调整反应物及溶剂与溶质的配比，研制出一套制备和提纯DAST晶体原料的工艺路线，提高原料的纯度和产率；并深入分析晶体的成核及其生长机理，改进晶体生长装置和工艺，拓宽溶液亚稳区宽度，提高溶液的稳定性，克服现有的DAST晶体自发成核生长模式的不足，可控生成高质量晶体，形成具有自主知识产权的发明专利。该系列工作对完善DAST原料制备工艺与晶体生长技术具有重要的理论意义和应用价值，对THz技术的发展也将起到推动作用。

太赫兹波所处的波谱范围，使其在能量、安全性及穿透性等方面发挥出独有的性质，在医学成像、安全检查、产品检测、空间通信、武器制导等方面具有重要的应用前景。但缺乏稳定、高效的太赫兹辐射源成为制约太赫兹技术发展的关键问题，迫切需要研究开发新一代的光电信息材料及其应用技术，特别是发展具有较大非线性光学系数和高电光性能的新材料。研究表明有机DAST晶体是构建太赫兹发射源的理想材料，但目前国内外市场尚无可用于研制DAST晶体生长所必需的原料出售，因此，制备满足晶体生长需求的高纯度原料是当务之急；其次，DAST晶体的生长技术还很薄弱，严重阻碍了基于DAST晶体的太赫兹技术的研究和应用开发。.针对以上问题，本研究自行合成出高纯的晶体生长原料；基于自发成核法、斜板法及籽晶法等晶体生长方法，设计研制出适合不同生长方法的晶体生长装置；测定了生长溶液的亚稳区，进行了晶体生长及其机理研究，通过不断优化生长工艺参数，解决了晶体生长过程中溶液稳定性变差的难题，形成一套成熟的晶体生长技术，实现了晶体的可控成核生长，制备出尺寸为17×18×2mm3的较高质量的DAST晶体，晶体透过率近80%。在此基础上，基于DAST晶体，采用光学差频法测得调谐曲线的调谐范围为0.51-19.69THz，在4.11THz处获得最高单脉冲能量267.7nJ，转换率为1.04×10-4，比文献报道的同种测试方法获得的转换效率有了较明显的提高。.该课题的研究将为高质量DAST晶体的生长提供优质原料，为高质量晶的生长提供重要保障，为解决我国应用于太赫兹辐射源的晶体材料短缺问题提供技术支持，对其它有机类晶体的生长也将具有重要的参考价值与指导意义。