Structural, electronic and magnetic properties of oxides at high pressures and temperatures: new polymorphs, new insights and new possible applications

在这个项目中，我们将研究在高压和高温条件下稳定的新型氧化物晶型的结构、电子、光学和磁性。本项目的总体科学目标如下：(I)寻找氧化物中新的高压高温(HP-HT)晶型。这些研究将包括在高达25 Gpa和高达2500 K的大容量多砧木细胞中合成HP-HT，以及在高达100 Gpa和高达3000 K的范围内，利用激光加热的可能性在钻石砧木细胞中进行原位高压研究(Ii)在对HP-HT处理后回收的样品进行的异地研究和原位高压研究中详细研究新的多晶型的物理性质。我们计划使用几种实验技术，如粉末和单晶X射线衍射，显微拉曼光谱，红外，近红外和可见光吸收光谱，微探针，扫描电子显微镜和透射电子显微镜分析，电子衍射，中子衍射，纳米压痕，电阻率测量，热电功率，霍尔效应，磁阻，磁化率，电极化和其他一些实验技术。在这个项目中，我们将调查在新的氧化铁Fe4O5、钙钛矿型Mn2O3和其他系统中发现的几种这样的情况。(Ii)我们制备和研究了几种可能在未来工业应用中有前途的新氧化物，例如可以广泛应用于半导体工业的新型硬直接带隙半导体，可能应用于磁性和压电元件的新型多铁性，以及广泛应用的新型智能材料。因此，本项目将对了解氧化物系统的物理做出重大贡献。一些发现也可能对工业应用产生影响。

In this project we will investigate structural, electronic, optical, and magnetic properties of new oxide polymorphs that are stabilized in conditions of high pressures and high temperatures (HP-HT). The overall scientific goals of the present project are as follows:(i) A search for new high-pressure high-temperature (HP-HT) polymorphs in oxides. These studies will include HP-HT synthesis in large-volume multi-anvil cells in ranges up to 25 GPa and up to 2500 K, as well as in-situ high-pressure studies in diamond anvil cells with a possibility of laser heating, in ranges up to 100 GPa and up to 3000 K.(ii) Detailed investigations of physical properties of new polymorphs in both ex-situ studies on samples recovered after HP-HT treatment and in in-situ high-pressure studies. We plan to use several experiment techniques, e.g., powder and single-crystal X-ray diffraction, micro-Raman spectroscopy, Infrared, near Infrared and visual absorption spectroscopy, micro-probe, SEM and TEM analyses, electron diffraction, neutron diffraction, nanoindentation, measurements of electrical resistivity, thermoelectric power, Hall effect, magnetoresistance, magnetic susceptibility, electrical polarization, and some others.The proposed work would have the following major implications:(i) New unusual materials prepared at HP-HT conditions often reveal new scientific puzzles that may play an important role in advancing the science. In this project we will investigate several such cases found in new iron oxide Fe4O5, perovskite-type Mn2O3, and in other systems. (ii) We prepare and investigate several new oxides that may be promising for future industrial applications, e.g. new hard direct-band gap semiconductors that can be widely used in semiconductor industry, new multiferroics for possible applications in magnetic and piezo- elements, new smart materials for a wide range of applications.Thus, this project should make a significant contribution to understanding of physics of oxide systems. Some findings can also have implications for industrial applications.