High-pressure synthesis and properties of novel simple oxides with unusual stoichiometries

最近发现和研究了化学计量比未知的新型简单铁氧化物(FeOy)(如Fe4O5、Fe5O6、Fe7O9等)，这些氧化物可以在高压高温(HP-HT)条件下合成，表明这些氧化物在自然科学中具有特殊的兴趣。与磁铁矿(Fe3O4)一样，这些混价的简单铁氧化物为研究电荷相互作用与物理性质之间的相互关系提供了理想的模型体系。特别是，在Fe_3O_4、Fe_4O_5和Fe_5O_6中发现的金属-绝缘体类型的电荷有序转变伴随着晶体结构的严重扭曲。本项目致力于铁、钛和锰三种常见过渡金属的新型简单氧化物的合成和物理性质的研究。我们将合成这些简单氧化物的新型混合价相，并研究它们在广泛的温度和压力范围内的电子、光学、振动、机械、磁性和其他性质。我们的研究将涉及各种实验技术，包括但不限于：单晶X射线衍射、中子衍射、穆斯堡尔光谱、拉曼光谱、红外和光学吸收光谱，以及不同物理特性的测量，如：电阻率、热电功率、磁化率、磁化强度、介电常数、电极化等。从基础性和应用性两个角度来看，这项研究似乎都非常重要。这些研究的结果将有助于理解更复杂、强相关的氧化物的物理性质。

Recent discoveries and studies of novel simple oxides of iron (FexOy) with hitherto unknown stoichiometries (e.g., Fe4O5, Fe5O6, Fe7O9, etc.), which can be synthesized at high-pressure high-temperature (HP-HT) conditions, showed that these oxides are of an exceptional interest for natural sciences. Alike magnetite (Fe3O4), these mixed-valent simple iron oxides present the perfect model systems to investigate the interrelations between the charge interactions and physical properties. In particular, the charge-ordering transitions of metal-insulator-type discovered in Fe3O4, Fe4O5 and Fe5O6 were found to be concurrent with extraordinary distortions in their crystal structures. The present project is dedicated to HP-HT synthesis and investigation of physical properties of novel simple oxides of three common transition metals, such as iron, titanium and manganese. We will synthesize novel mixed-valence phases of these simple oxides and investigate their electronic, optical, vibrational, mechanical, magnetic, and other properties in the wide ranges of temperatures and applied pressures. Our research will involve a variety of experimental techniques including but not limited to: single crystal X-ray diffraction, neutron diffraction, Mössbauer spectroscopy, Raman spectroscopy, Infrared and optical absorption spectroscopy, and measurements of different physical characteristics, such as: electrical resistivity, thermoelectric power, magnetic susceptibility, magnetization, dielectric constant, electric polarization, and others. This study seems to be highly important from both fundamental and applied perspectives. Results of these investigations would facilitate an understanding of physical properties of more complex strongly correlated oxides.