Development of simultaneous measurements system of electric conductivity and x-ray diffraction on mantle minerals at high pressure and temperature

高压高温地幔矿物电导率和X射线衍射同步测量系统研制

• 批准号: 15340187
• 负责人: NAGAI Takaya
• 金额: $ 9.98万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15340187/
• 关键词: electric conductivity; x-ray diffraction; measurement system; high pressure; ulvospinel; magnetite; diamond anvil cell; phase transition; 電気伝導度; ホッピング; 装置開発; Fe304; Fe2TiO4; electric conductivity; x-ray diffraction; measurement system; high pressure; ulvospinel; magnetite; diamond anvil cell; phase transition; 電気伝導度; ホッピング; 装置開発; Fe304; Fe2TiO4

A diamond anvil cell, which can apply to electric resistance and x-ray diffraction measurements simultaneously, was designed in this research project. The DAC is basically modified the lever & spring type DAC and two electrodes model for electric resistance measurements is installed the DAC.A series of single crystals of the magnetite (Fe_3O_4)-ulvospinel (Fe_2TiO_4) solid solution were synthesized by the FZ method. Then, electric resistance measurements were performed on those samples and x-ray diffraction measurements were also performed at the same time.Electric resistances on all samples decrease gradually with increasing pressure probably due to the electron hopping and the band overlapping mechanism. However, the electric resistances suddenly show no pressure-dependency-above some critical pressures. The critical pressure increases with iron content in the solid solution of Fe_<3-x>Ti_xO_4. For example, the critical pressures are about 6.5GPa for Fe_2TiO_4 and about 24GPa for Fe_3O_4. X-ray powder diffraction patterns obtained above the critical pressure showed that some single diffraction peaks split into doublet peaks above the critical pressure. The evidence suggests a structural transition occurs at the critical pressure. According to the single crystal structure analysis experiments on Fe_2TiO_4 at high pressure, the structural transition could be assigned as the transition from cubic to tetragonal symmetry and the Mn_3O_4 type structure can be proposed as a candidate of the high-pressure form of Fe_2TiO_4. The newly designed system in this research project can provide some interesting and important information about the relationship between the crystal structures and electric resistances.

该研究项目设计了一个同时适用于电阻和X射线衍射测量值的钻石砧细胞。 DAC基本修改了杠杆和弹簧型DAC，并安装了两个用于电阻测量的电极模型。磁铁矿（FE_3O_4）的一系列单晶（FE_3O_4）-Ulvospinel（FE_2TIO_4）实心溶液通过FZ方法合成。然后，对这些样品进行了电阻测量，并在同一时间进行X射线衍射测量。所有样品的电阻逐渐随着压力增加而逐渐减小，这可能是由于电子跳跃和带重叠的机制。但是，电阻突然没有压力依赖性 - 一些临界压力。临界压力随着fe_ <3-x> ti_xo_4的固体溶液中的铁含量而增加。例如，对于Fe_2Tio_4的关键压力约为6.5GPA，Fe_3O_4的关键压力约为24GPA。在临界压力上方获得的X射线粉末衍射模式表明，某些单个衍射峰分为临界压力上方的双重峰。证据表明结构过渡发生在临界压力下。根据FE_2TIO_4在高压下的单晶结构分析实验，可以将结构过渡分配为从立方体到四方对称性的过渡，并且可以提出MN_3O_4类型结构作为FE_2TIO_4的高压形式的候选。该研究项目中新设计的系统可以提供一些有趣而重要的信息，以了解晶体结构与电阻之间的关系。