Design and melt growth for novel photonic crystals by micro pulling down method

本论文的研究课题是光子晶体的光学创新。为了实现基于纳米技术的光子晶体新特性的块体材料的开发，我们通过计算机模拟进行了材料设计的建立，在计算流体力学计算程序中考虑了微重力条件下出现的Marangoni对流现象，并在此基础上提出了基于微下拉法的高速熔体生长方法和光子带隙的评价方案（有限体积法），建立了一种高精度的模拟技术。提出了一种新的大直径高质量单晶体对流控制方法--可调旋转环提拉法（ARRCZ），并对该方法控制的籽晶生长速度的稳定性、固液界面的光滑性和对流进行了研究，采用微下拉法生长了Eu 3+材料。以Al_2O_3和Y_2O_3等4 N粉末的化学计量比混合物为原料，进行预烧。在惰性气氛下使用晶种用Ir坩埚进行生长。近年来，我们研制了Al_2O_3/Y_3Al_5O_2<12>、Al_2O_3/Y_3Al_5O_2<12>/ZrO_2和MgAl_2O_4/MgO等共晶材料，并对其性能进行了研究。结果表明，影响显微组织的因素是多方面的。材料体系、杂质和生长速度是影响生长的主要因素。在MgAl_2O_4/MgO体系中，MgO在基体中呈规则分布，酸对MgO部分有选择性刻蚀。

In the present study, our research topic is photonic crystal for optical innovation. In order to realize a development of bulk materials based on novel properties of photonic crystal by nanotechnology, we performed establishment of materials design by computer simulation, high speed melt growth by micro pulling down method and evaluation scheme for photonic band gap based on the calculation results.The Marangoni convection that appeared under the microgravity condition was taken into account to computational fluid dynamics calculation code (finite volume method) for a conventional Czochralski method and the micro pulling down method, and a high accuracy simulation technique was established. We proposed Adjustable Rotating Ring Czochralski method(ARRCZ) that is a new convection control method for a large diameter high-quality single crystal, the stability of the growth speed of the seed crystal by this control method, the smoothness of the interface of solid and liquid phases, and convection were examined, and these results reveal for the best single crystal growth condition in this year.Eutectic materials were grown by the micro pulling down method. Stoichiometric mixture of 4N powder such as Al_2O_3 and Y_2O_3 were used as starting materials and preliminary sintered. The growth was carried with Ir crucible under inert atmosphere using seed crystals. This year several eutectic materials such as Al_2O_3/Y_3Al_5O_<12>, Al_2O_3/Y_3Al_5O_<12>/ZrO_2 and MgAl_2O_4/MgO have grown and properties were investigated. As a result, factors to influence micro structure were clarified. Material systems, impurities and growth speed were especially effective factors. In MgAl_2O_4/MgO system, regular pattern of MgO in the matrix was observed and MgO part was selectively etched by acid.