Crystal growth of functional and multi-functional oxides

对气候变化、环境和能源效率的关注，使人们的注意力集中在寻找具有新的或更好的功能的材料上。功能材料的物理和化学性质会随着外界刺激而变化，如电场和磁场、温度、压力、光照或原子和分子的吸附。功能材料的重要例子有热电材料、铁电材料、多铁材料、磁场传感器、压电材料、快离子导体和超导体。设计更好的功能材料需要了解它们的工作原理。为了揭开它们的秘密，我们需要在具有高度纯度和晶体完整性的单晶上进行实验。需要单晶形式的样品，因为大多数功能材料是晶体，它们的性质随着晶体中的方向而变化。在这个项目中，我将生长选定的热电、磁电和超导材料的单晶，然后通过与各种实验技术的专家合作，进行实验研究，以揭示这些材料的性质，并为测试它们的行为模型提供数据。我将集中讨论的材料都是氧化物，其性质是由电子之间的相互作用驱动的。它们根据其功能分为三类：(1)热电材料--其性质使其能够将废热转化为能量或直接将电用于制冷和加热；(2)磁电材料--允许通过电场控制磁的材料；(3)超导体--可以无电阻地导电的材料。高质量的大块复杂材料单晶的生长是一项需要特殊技术和设备的高级研究活动。我将在使用光作为热源的镜面熔炉中使用一种称为浮区法的方法。通过对生长条件的实验，我希望能够生长出非常高质量的晶体，供我的合作者在实验中用来探索其物理性质背后的机制。

Concern over climate change, the environment and energy efficiency, has focused attention on the search for materials with new or better functionality. Functional materials have physical and chemical properties which change in response to external stimuli, such as electric and magnetic fields, temperature, pressure, exposure to light, or adsorption of atoms and molecules. Important examples of functional materials are thermoelectrics, ferroelectrics, multiferroics, magnetic field sensors, piezoelectric materials, fast-ion conductors, and superconductors. The design of better functional materials requires an understanding of how they work. To uncover their secrets, we need to perform experiments on single crystals with a high degree of purity and crystalline perfection. Samples in the form of single crystals are needed because most functional materials are crystalline and their properties vary with direction in the crystal.In this project I will grow single crystals of selected thermoelectric, magnetoelectric and superconducting materials then, through collaboration with experts in various experimental techniques, experimental investigations will be performed in order to uncover the properties of these materials and to provide data to test models for their behaviour.The materials I will concentrate are all oxides whose properties are driven by interactions between the electrons. They divide into 3 classes according to their function:(1) thermoelectrics - materials whose properties allow them to convert waste heat into energy or to use electricity directly for cooling and heating,(2) magnetoelectrics - materials which permit control of magnetism by electric fields and vice versa,(3) superconductors - materials which can conduct electricity without resistance.The growth of high quality bulk single crystals of complex materials is an advanced research activity requiring special techniques and equipment. I will use a method called the floating-zone method in a mirror furnace which uses light as the heat source. By experimenting with the growth conditions I hope to be able to grow crystals of very high quality which can be used by my collaborators in experiments to probe the mechanisms behind their physical properties.