Advanced Inorganic Functional Materials: Floating Zone Crystal Growth System

新的无机功能材料的开发，需要一系列的应用，需要了解候选相的结构和物理性质。在结构方面，高质量的大（厘米大小）单晶是解决和改进这类材料结构的最佳样品。原因有两方面。首先，与粉末衍射相比，单晶衍射的优点在于可以可靠地测量单个布拉格反射的强度，而粉末衍射则存在峰重叠的问题。其次，中子衍射是确定功能材料结构的首选方法，其中x射线散射主要由较重的阳离子主导，阴离子的关键信息（原子位置、占位、热位移参数）无法可靠地确定。此外，中子衍射还可以探测远程磁序。由于物质与中子的相互作用相对于x射线弱，所以需要大的单晶。对于物理性质测量，与使用粉末样品相比，大的单晶具有几个优点。例如，晶体可以相对于实验探针定向，以便研究物理性质（如电或磁响应）的方向性和各向异性。此外，对多晶动力材料的性能测量经常受到晶界效应的影响，而晶界效应不能总是与材料本体的响应分离。在这个项目中，我们将建立一个浮区晶体生长系统，以生产一系列重要无机材料的高质量样品。这些材料包括能源应用材料（燃料电池、光伏、热电）和那些电子或磁有序直接导致可开发特性的材料，如压电、传感、水下和医学成像、气体分离、忆阻器和多铁存储器应用。我们获得的有关结构和物理性质的信息将有助于这些化合物的开发，并为我们设计新一代改进功能材料提供所需的见解。

The development of new inorganic functional materials, needed for a range of applications, requires the understanding of structures and physical properties of the candidate phases. On the structural side, high-quality large (cm-sized) single crystals are the best samples on which to solve and refine structures of such materials. The reason for this is two-fold. Firstly, single crystal diffraction has the advantage over powder diffraction in that the intensities of individual Bragg reflections can be measured reliably, whereas the latter suffers from peak overlap. Secondly, neutron diffraction is the method of choice for structure determination of functional materials in which the X-ray scattering is dominated by heavier cations and key information (atomic positions, occupancies, thermal displacement parameters) about the anions cannot be determined reliably. In addition, neutron diffraction can also probe long-range magnetic order. Large single crystals are needed due to the weaker interaction of matter with neutrons relative to X-rays. For physical property measurements, large single crystals offer several advantages compared to working with powdered samples. For example, crystals can be oriented with respect to experimental probes in order to investigate the directionality and anisotropy of physical properties such as electrical or magnetic responses. In addition, property measurements on polycrystalline powered materials often suffer from grain boundary effects, which cannot always be separated from the response of the bulk of the material.In this project we will establish a floating zone crystal growth system to produce high-quality samples of a range of important inorganic materials. These include materials for energy applications (fuel cells, photovoltaics, thermoelectrics) and those where electronic or magnetic ordering leads directly to exploitable properties such as piezoelectricity, sensing, under-water and medical imaging, gas separation, memristor and multiferroic memory applications. The information we gain on the structures and physical properties will help the exploitations of these compounds and give us the insight needed to design new generation of improved functional materials.