温度诱导的A-B站间电荷转移在一个A站点排序的LaCu(3)Fe(4)O(12) 矿中
1Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan. ywlong@msk.kuicr.kyoto-u.ac.jp
Nature
|March 6, 2009
概括
研究人员在LaCu(3)Fe(4)O(12) 中发现了温度诱导的价值变化. 这种过渡涉及站点间的电荷转移,导致结构性,磁性和电气性质的显著变化,包括负热膨胀.
科学领域:
- 材料科学 材料科学 材料科学
- 固态化学 固态化学
- 凝聚物质物理学 凝聚物质物理学
背景情况:
- 过渡金属氧化物的价值状态变化显著改变结构和物理性质.
- 化学兴奋剂是调整价值状态的标准方法,通常会导致ABO(3) 矿具有奇特的特性.
- 通过电荷转移的外部诱导的价值变化很少见,通常需要极端条件.
研究的目的:
- 为了研究温度诱导的价值变化和A位点排序的双矿的位点间电荷转移.
- 探索结构性,磁性和运输性质的变化.
- 评估技术应用的潜力,特别关注负热膨胀.
主要方法:
- 合成和表征A位点排序的双矿LaCu(3)Fe(4)O(12).
- 温度依赖测量以观察相位转换和属性变化.
- 对价值状态和位置间电荷转移机制的分析.
主要成果:
- 在393K观察到一级的可逆转变,涉及A位 (Cu) 和B位 (Fe) 离子的价值变化.
- 确定了Cu和Fe之间的位置间电荷转移,导致从LaCu(2+) ((3) Fe(3.75+) ((4) O(12) 过渡到LaCu(3+) ((3) Fe(3+) ((4) O(12).
- 证明了相关的同结构相位过渡,从偏磁性到抗铁磁性和金属到绝缘状态,伴随着大负热膨胀.
结论:
- 3Fe4O12表现出独特的温度诱导的价值变化和位置间的电荷转移.
- 这些变化导致了磁性,电性和结构性质的显著变化.
- 观察到的室温以上转变与负热膨胀对技术应用具有前景.
更多相关视频
相关概念视频
02:54Trends in Lattice Energy: Ion Size and Charge
23.4K
An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure of the strength of this attraction. The lattice energy (ΔHlattice) of an ionic compound is defined as the energy required to separate one mole of the solid into its component gaseous ions. For the ionic solid sodium chloride, the lattice energy is the enthalpy change of the process:
23.4K
02:42Ionic Crystal Structures
18.0K
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
18.0K
02:42Valence Bond Theory
8.9K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
8.9K
02:58Crystal Field Theory - Octahedral Complexes
28.4K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
28.4K
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
47.5K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than...
47.5K
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
143
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
143