超伝導性は,高圧下で合成されたLaT (M) BNとLa3T (M2) B2N3 (T (M) =移行金属) で表される
Naoki Imamura1, Hiroshi Mizoguchi, Hideo Hosono
1Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
Journal of the American Chemical Society
|January 28, 2012
まとめ
新しい層状のボロニトリドは,6.7Kまでの臨界温度で,大量超伝導性を示します.これらの材料は,移行金属-ボロン相互作用から生じるユニークな電子構造を特徴とし,その超伝導性および磁気性に影響します.
科学分野:
- マテリアルサイエンス 材料科学
- 固体物理 固体物理学
- 無機化学 無機化学とは
背景:
- 層状ボロニトリドは,電子や超伝導性における潜在的な応用を持つ興味深い材料のクラスです.
- 結晶構造,電子状態,物理的性質の関係を理解することは,新しい材料を設計する上で極めて重要です.
研究 の 目的:
- 新しい層状ボロニトリドを一般式 (LaN) ((n) ((T)) ((M2) B ((2))) で合成し,特徴づけること.
- 電子構造とその超伝導性および磁性特性との相関を調査する.
- これらの材料の超伝導性の可能性を調査する.
主な方法:
- 層状のボロニトリドを準備するために,高圧合成技術が採用されました.
- 密度関数理論 (DFT) の計算を行い, (BN) ユニットと (LaN) 層の電子状態を分析しました.
- 合成化合物について,超伝導的移行温度 (T(c)) を測定した.
主要な成果:
- LaNiBN,CaNiBN,およびLaPtBNを含むいくつかの層状のボロニトリドが成功裏に合成されました.
- 大量超伝導性は,LaNiBN (T(c) ≈4.1 K),CaNiBN (T(c) ≈2.2 K,およびLaPtBN (T(c) ≈6.7 Kで観察されました.
- DFTの計算により,フェルミレベルはT (M) (d) -B (p) のアンチボンドング帯に位置し,主なT (M) (d) の帯はE (F) の下にあることが明らかになった.
- 非超伝導性化合物は,強い共電結合からの移動電子によるパウリパラマグネティックな行動を示した.
結論:
- 合成された層状のボロニトリドは,有望な超伝導特性を示しています.
- 電子構造,特にT (M) (d) -B (p) 相互作用は,超伝導性と磁気行動を決定する上で重要な役割を果たします.
- これらの発見は,層状のボルニトリド構造に基づいた高温超伝導体に関するさらなる研究への道を開きます.
関連する概念動画
01:24Superconductor
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a superconductor. In 1911, Heike Kamerlingh Onnes of Leiden University, a Dutch physicist, observed a relation between the temperature and the resistance of the element mercury. The mercury sample was then cooled in liquid helium to study the linear dependence of resistance on temperature. It was observed that, as the temperature decreased, the...
01:28Types Of Superconductors
A superconductor is a substance that offers zero resistance to the electric current when it drops below a critical temperature. Zero resistance is not the only interesting phenomenon as materials reach their transition temperatures. A second effect is the exclusion of magnetic fields. This is known as the Meissner effect. A light, permanent magnet placed over a superconducting sample will levitate in a stable position above the superconductor. High-speed trains that levitate on strong...
02:32Bonding in Metals
Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Drüde called the “Electron Sea Model”.
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:58Properties of Transition Metals
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
02:42Valence Bond Theory
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...