Local structures and electoric conduction mechanism of minerals in Earth's lower mantle.

(Mg Fe，Al）（Si，Al）O3钙钛矿和（Mg，Fe）O镁方铁矿被认为是地球下地幔的主要成分。众所周知，地球下地幔具有高电导率（1-10 S/m）。局域结构的知识对于理解复杂的物理性质是至关重要的。利用EXAFS技术可以研究非简谐有效对势。势函数的非谐性与材料的热膨胀、热导率和离子电导率等物理性质有直接的关系。我们精确地重新研究了这些下地幔矿物和类似物的单晶的导电性和导电机制。地球内部材料的单晶是在高压和高温（例如25 GPa，2000 K和0.1MPa，3000 K）下用各种方法生长的。在各种条件和气氛下通过复阻抗法测量电导率。精密C ...更多信息 利用EXAFS谱和衍射方法揭示了地幔中镁橄榄石石榴石、镁方石英、MgSiO_3钙钛矿固溶体和方石英等多种物质的晶体结构和热性质，估算了高温高压下发现势垒处移动的离子的可能性。在最高温度下，在超离子导电矿物中，在势垒处发现移动的离子的概率大于百分之几。测量了MgSiO 3钙钛矿固溶体的类似物的电导率，并显示钙钛矿型化合物在其熔点附近成为具有离子导电性的固体电解质。明确了钙钛矿型化合物的本征导电激活能约为2.0 eV。该值表示空位形成能和空位迁移能的总和，其中空位形成能约为1.0 eV。在这项研究中，揭示了地球下地幔的高电导率不能用钙钛矿晶体的本征导电机制来解释。下地幔中的可能机制被认为是（Mg，Fe，Al）（Si，Al）O3钙钛矿与共晶反应的外生离子导电或（Mg，Fe）O镁方铁矿通过大极化子的导电。少

(Mg, Fe, Al)(Si, Al) O3 perovskite and (Mg, Fe) O magnesio-wustite are believe to major components of the Earth's lower mantle. It is well known that the Earth's lower mantle exhibits high electric conductivity (1-10 S/m). The knowledge of the local structure is of primary importance for the understanding of the complicated physical properties. An anharmonic effective pair potential can be investigated using the EXAFS technique. The anharmonicity in potentials is directory correlated with physical properties such as the thermal expansion, thermal conductivity and ionic conductivity. We have precisely reinvestigated the conductivity and conduction mechanism of single crystals of such lower mantle minerals and analogues.Single crystals of the Earth's internal materials were grown by various methods under high-pressure and high -temperature (e.g. 25 GPa, 2000 K and 0.1 MPa, 3000 K). Conductivity was measured by a complex impedance method under various conditions and atmospheres. Precise c … More rystal structure and thermal properties for many materials in the Earth's mantle such as majorite garnet, magnesio -wustite, MgSiO3 perovskite solid -solution and stishovite have been revealed by EXAFS spectroscopy and diffraction method.The probability of finding mobile ions at potential barrier was estimated under high temperature and high pressure by EXAFS spectroscopy. The probability of finding mobile ions at potential barrier is larger than several percent in superionic conducting minerals at the highest temperature. Conductivities of analogues of MgSiO3 perovskite solid-solution were measured and showing that the perovskite type compound became solid electrolytes with ionic conduction near their melting points. It was clarified that activation energies for intrinsic conduction of perovskite type compounds are about 2.0 eV.The value indicates the summation of the vacancy formation energy and the vacancy migration energy, where the vacancy formation energy is about 1.0 eV.In this study, it was revealed that the high conductivity in Earth's lower mantle cannot explained by the intrinsic conduction mechanism of perovskite crystals. Possible mechanism in the lower mantle is considered as extrinsic ionic conduction of (Mg, Fe, Al)(Si, Al) O3 perovskite with eutectic reactions or as a conduction of (Mg, Fe) O magnesio-wustite by a large polaron. Less