{"title":"高压下 FeTiO_3 结构转变中各向异性的导电率变化","authors":"Takamitsu Yamanaka, Yuki Nakamoto, Masafumi Sakata, Katsuya Shimizu, Takanori Hattori","doi":"10.1007/s00269-023-01261-6","DOIUrl":null,"url":null,"abstract":"<div><p>Electrical resistivity measurements on oriented FeTiO<sub>3</sub> ilmenite using single crystals at high pressures proves that FeTiO<sub>3</sub> ilmenite shows anisotropic electrical resistivity. The resistivity in the direction perpendicular to the <i>c</i>-axis decreased monotonously with increasing pressure. In contrast, the resistivity in the parallel direction to the <i>c</i>-axis initially decreased and slightly increased with increasing pressure above 6 GPa. It then resumed decreasing above 8 GPa. The hallow-shape of the curvature was observed. Neutron and synchrotron X-ray diffraction experiments provided an accurate picture of the pressure-induced changes of the FeTiO<sub>3</sub> ilmenite structure. FeTiO<sub>3</sub> transforms neither into perovskite nor LiNbO<sub>3</sub> phase under pressures up to 28 GPa. However, different compression curves were observed for both FeO<sub>6</sub> and TiO<sub>6</sub> octahedra below 8 GPa. FeO<sub>6</sub> is more compressible and flexible than TiO<sub>6</sub>. Among Fe–Fe, Ti–Ti and Fe–Ti interatomic distances, the shortest Fe–Ti distance presents the highest electrical restivity and electron mobility according to Fe<sup>2+</sup>Ti<sup>4+</sup> and Fe<sup>3+</sup>Ti<sup>3+</sup> by electron super-exchange mechanism, which is enhanced during compression. At high pressure, the electron configuration of Fe<sup>2+</sup> (3<i>d</i><sup>6</sup>) is more strongly changed than Ti<sup>4+</sup> (3<i>d</i><sup>0</sup>) and the former cation is the emphasized by Jahn–Teller effect in the ligand field of <i>C</i><sub>3<i>v</i></sub> molecular symmetry. The anisotropic electrical resistivity and non-uniform structure change of Fe–Ti interatomic distance can be explained by possible spin transition. The spin transition of Fe<i>Kβ</i> from high-spin to intermediate-spin state is possible in the electronic state change of FeTiO<sub>3</sub>.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Anisotropic electrical conductivity changes in FeTiO3 structure transition under high pressure\",\"authors\":\"Takamitsu Yamanaka, Yuki Nakamoto, Masafumi Sakata, Katsuya Shimizu, Takanori Hattori\",\"doi\":\"10.1007/s00269-023-01261-6\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Electrical resistivity measurements on oriented FeTiO<sub>3</sub> ilmenite using single crystals at high pressures proves that FeTiO<sub>3</sub> ilmenite shows anisotropic electrical resistivity. The resistivity in the direction perpendicular to the <i>c</i>-axis decreased monotonously with increasing pressure. In contrast, the resistivity in the parallel direction to the <i>c</i>-axis initially decreased and slightly increased with increasing pressure above 6 GPa. It then resumed decreasing above 8 GPa. The hallow-shape of the curvature was observed. Neutron and synchrotron X-ray diffraction experiments provided an accurate picture of the pressure-induced changes of the FeTiO<sub>3</sub> ilmenite structure. FeTiO<sub>3</sub> transforms neither into perovskite nor LiNbO<sub>3</sub> phase under pressures up to 28 GPa. However, different compression curves were observed for both FeO<sub>6</sub> and TiO<sub>6</sub> octahedra below 8 GPa. FeO<sub>6</sub> is more compressible and flexible than TiO<sub>6</sub>. Among Fe–Fe, Ti–Ti and Fe–Ti interatomic distances, the shortest Fe–Ti distance presents the highest electrical restivity and electron mobility according to Fe<sup>2+</sup>Ti<sup>4+</sup> and Fe<sup>3+</sup>Ti<sup>3+</sup> by electron super-exchange mechanism, which is enhanced during compression. At high pressure, the electron configuration of Fe<sup>2+</sup> (3<i>d</i><sup>6</sup>) is more strongly changed than Ti<sup>4+</sup> (3<i>d</i><sup>0</sup>) and the former cation is the emphasized by Jahn–Teller effect in the ligand field of <i>C</i><sub>3<i>v</i></sub> molecular symmetry. The anisotropic electrical resistivity and non-uniform structure change of Fe–Ti interatomic distance can be explained by possible spin transition. The spin transition of Fe<i>Kβ</i> from high-spin to intermediate-spin state is possible in the electronic state change of FeTiO<sub>3</sub>.</p></div>\",\"PeriodicalId\":20132,\"journal\":{\"name\":\"Physics and Chemistry of Minerals\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.2000,\"publicationDate\":\"2024-02-05\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Physics and Chemistry of Minerals\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s00269-023-01261-6\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"MATERIALS SCIENCE, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-023-01261-6","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
Anisotropic electrical conductivity changes in FeTiO3 structure transition under high pressure
Electrical resistivity measurements on oriented FeTiO3 ilmenite using single crystals at high pressures proves that FeTiO3 ilmenite shows anisotropic electrical resistivity. The resistivity in the direction perpendicular to the c-axis decreased monotonously with increasing pressure. In contrast, the resistivity in the parallel direction to the c-axis initially decreased and slightly increased with increasing pressure above 6 GPa. It then resumed decreasing above 8 GPa. The hallow-shape of the curvature was observed. Neutron and synchrotron X-ray diffraction experiments provided an accurate picture of the pressure-induced changes of the FeTiO3 ilmenite structure. FeTiO3 transforms neither into perovskite nor LiNbO3 phase under pressures up to 28 GPa. However, different compression curves were observed for both FeO6 and TiO6 octahedra below 8 GPa. FeO6 is more compressible and flexible than TiO6. Among Fe–Fe, Ti–Ti and Fe–Ti interatomic distances, the shortest Fe–Ti distance presents the highest electrical restivity and electron mobility according to Fe2+Ti4+ and Fe3+Ti3+ by electron super-exchange mechanism, which is enhanced during compression. At high pressure, the electron configuration of Fe2+ (3d6) is more strongly changed than Ti4+ (3d0) and the former cation is the emphasized by Jahn–Teller effect in the ligand field of C3v molecular symmetry. The anisotropic electrical resistivity and non-uniform structure change of Fe–Ti interatomic distance can be explained by possible spin transition. The spin transition of FeKβ from high-spin to intermediate-spin state is possible in the electronic state change of FeTiO3.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)