在极地迪昂-雅各布森氧化物RbNdTa2O7中的结构扭曲和单轴负热膨胀
P Neenu Lekshmi1, E Lora da Silva1,2, P Rocha-Rodrigues1
1IFIMUP, Institute of Physics for Advanced Materials, Nanotechnology and Photonics, Department of Physics and Astronomy, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
概括
在RbNdTa2O7的I2cm到Cmce阶段过渡过程中,RbNdTa2O7表现出单轴负热膨胀 (NTE),由NdTa2O6层收缩驱动. 这与典型的机制形成鲜明对比,并揭示了极性氧化物中复杂的相互作用.
科学领域:
- 固态化学和物理 固态化学和物理
- 材料科学是一种材料科学.
- 结晶学和相位过渡.
背景情况:
- 迪昂-雅各布森相是层层的矿氧化物,在电子领域有潜在的应用.
- 了解结构相变和热膨胀对于材料设计至关重要.
- RbNdTa2O7是一种n=2的迪昂-雅各布森极性氧化物,其特性尚不清楚.
研究的目的:
- 研究RbNdTa2O7.7的晶体结构,相变,热膨胀和电子特性.
- 阐明观察到的负热膨胀 (NTE) 背后的机制.
- 探索结构变化和电子行为之间的关系.
主要方法:
- 用于结构分析的X射线粉碎衍射 (XRPD) 和中子粉碎衍射 (NPD).
- 温度依赖的拉曼光谱法用于研究相位过渡.
- 密度函数理论 (DFT + U) 对电子属性的计算.
主要成果:
- 观察到的顺序相变:I2cm → Cmce → I4/mcm → P4/mmm.
- 在第一阶段I2cm → Cmce过渡过程中确定了单轴负热膨胀 (NTE),归因于NdTa2O6层收缩.
- 确定 I4/mcm → P4/mmm 过渡发生在 1150 K 左右通过 NPD.
- DFT+U的计算提供了对极地基态的电子性质的见解.
结论:
- RbNdTa2O7中的NTE与离子的极向反极移位以及特定的TaO6扭曲有关.
- 观察到的NTE机制与Ruddlesden-Popper阶段的不同,突出了Dion-Jacobson化合物的独特行为.
- 拉曼光谱证实了第一阶段的转变,并表明了债券刚度的增加.
相关概念视频
Thermal Expansion
5.6K
The expansion of alcohol in a thermometer is one of many commonly encountered examples of thermal expansion, which is the change in size or volume of a given system as its temperature changes. The most visible example is the expansion of hot air. When air is heated, it expands and becomes less dense than the surrounding air, which then exerts an upward force on the hot air to, for example, make steam and smoke rise, and hot air balloons float. The same behavior happens in all liquids and gases,...
5.6K
Thermal expansion and Thermal stress: Problem Solving
2.1K
San Francisco's Golden Gate Bridge is exposed to temperatures ranging from -15 °C to 40 °C. At its coldest, the main span of the bridge is 1275 m long. Assuming that the bridge is made entirely of steel, what is the change in its length between these temperatures?
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55...
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55...
2.1K
Molecular Shape and Polarity
74.7K
Dipole Moment of a Molecule
74.7K
Group Polarization
38.4K
Group polarization is the strengthening of an original group attitude following the discussion of views within a group (Teger & Pruitt, 1967). That is, if a group initially favors a viewpoint, after discussion the group consensus is likely a stronger endorsement of the viewpoint. Conversely, if the group was initially opposed to a viewpoint, group discussion would likely lead to stronger opposition.
38.4K
Oxidation Numbers
42.3K
In redox reactions, the transfer of electrons occurs between reacting species. Electron transfer is described by a hypothetical number called the oxidation number (or oxidation state). It represents the effective charge of an atom or element, which is assigned using a set of rules.
42.3K
Oxidation-Reduction Reactions
75.2K
Oxidation–Reduction Reactions
75.2K


