Crystal Growth Technique and New Development by Floating Zone Method for Functional Oxide Single Crystals

摘要

Single crystals are substances where the atoms are arranged with regularity in three dimensions, and contain no grain boundary or voids unlike sintered materials. The single crystals are indispensable for the important measurement of properties to clarify the superconductivity theory and R&D of novel materials from the viewpoint of clarification of the intrinsic nature and the anisotropy of substances. In reality, crystals such as sapphires and rubies produced in nature include many impurities and defects and greatly vary in quality. The selection of shapes and crystallographic orientation in the natural crystals was restricted to specific areas. For these reasons, in the past these natural crystals were scarcely used in electronic and optical industrial materials. Since then, due to the development of crystal growth techniques, high purity and less defective single crystals have been produced on a massive scale, and have brought about a major innovative change in the electronics industry in the 20th century. Quartz crystals are quoted as the typical example. As a result the synthetic quartz crystals were grown successfully by a hydrothermal method and the synthetic quartz crystals are used for application in IT-related devices such as computers and mobile phones as well as clocks. And also single crystals of synthesized materials, which are not produced in nature, such as Lithium niobate (LiNbO_3) and Yttrium aluminum garnet (Y_3Al_5O_(12)) can be grown, and have high-performance and novel function that was impossible to achieve with mineral crystals. These materials can be used for application in electronic and optical materials such as a laser material, a surface acoustic wave device material and an electro-optics device material.