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在YbGaGe中由于电子价值过渡而导致零热膨胀
James R Salvador1, Fu Guo, Tim Hogan
1Department of Chemistry and Centre for Fundamental Materials Research, Michigan State University, East Lansing, Michigan 48824, USA.
Nature
|October 17, 2003
概括
研究人员发现了一种新材料,Ytterbium Gallium Germanide (YbGaGe),具有接近零的热膨胀 (ZTE). 这种导电化合物在广泛的温度范围内显示的体积变化微不足道,这可能会消除对复杂复合材料的需求.
科学领域:
- 材料科学 材料科学 材料科学
- 凝聚物质物理学 凝聚物质物理学
- 固态化学 固态化学
背景情况:
- 大多数材料在加热时膨胀,但有些材料在单一晶体学方向呈现负热膨胀 (NTE).
- 负热膨胀材料很少见,包括,和某些合金和复合材料.
- 零热膨胀 (ZTE) 复合材料是通过结合正和负热膨胀材料来制造的,以防止热冲击.
研究的目的:
- 研究一种具有零热膨胀 (ZTE) 的纯材料的潜力.
- 为了探索导电性金属间化合物YbGaGe.Ge的特性.
- 为了确定YbGaGe是否在实际温度范围内表现出微不足道的体积变化.
主要方法:
- 合成和表征金属间化合物YbGa.Ge.Ge的合成和表征.
- 测量YbGaGe在100K和400K之间的热膨胀特性.
- 分析材料的电导率和结构行为与温度.
主要成果:
- YbGaGe几乎呈现零热膨胀 (ZTE),在100K和400K之间体积变化微不足道.
- 该材料具有导电性,使其适合各种应用.
- 在Yb原子中,温度诱导的价值过渡被提出为观察到的ZTE行为机制.
结论:
- YbGaGe为纯零热膨胀 (ZTE) 材料提供了一个有希望的候选者.
- 这一发现可以消除对ZTE复合材料的需求,简化材料设计.
- 潜在的应用包括太空系统和热力学执行器,需要在温度波动下保持稳定.
相关概念视频
Ionization Energy
The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy (IE1). The first ionization energy for an element, X, is the energy required to form a cation with 1+ charge:
Fermi Level
The Fermi-Dirac function is represented by an S-shaped curve indicating the probability of an energy state being occupied by an electron at a given temperature. The Fermi level is the energy level at which there is a fifty percent chance of finding an electron, and it is positioned between the lower-energy valence band and the higher-energy conduction band.
At absolute zero temperature, electrons fill all energy states up to the Fermi level, leaving upper states empty. As the temperature rises,...
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Fermi Level Dynamics
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
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Semiconductors
There is variation in the electrical conductivity of materials - metals, semiconductors, and insulators that are showcased with the help of the energy band diagrams.
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Types of Semiconductors
Intrinsic semiconductors are highly pure materials with no impurities. At absolute zero, these semiconductors behave as perfect insulators because all the valence electrons are bound, and the conduction band is empty, disallowing electrical conduction. The Fermi level is a concept used to describe the probability of occupancy of energy levels by electrons at thermal equilibrium. In intrinsic semiconductors, the Fermi level is positioned at the midpoint of the energy gap at absolute zero. When...
Biasing of Metal-Semiconductor Junctions
Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
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