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ON MICROSTRUCTURE AND ELECTRONIC PROPERTIES OF BORON CARBIDE

机译:论硼化碳的组织和电子性质

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Boron carbide (homogeneity range B_(4.3)C - B_(11)C) exhibits ~ 15 atoms per elementary cell and is composed of B_(12) or B_(11)C icosahedra and linear structure elements CBC, CBB or BOB (□, vacancy), whose shares depend on the chemical composition. Their random distribution excludes x-ray diffraction and NMR from structure analysis. Phonon spectroscopy on isotopically pure boron carbide solves this problem. - Experimental investigations established semiconducting character. They contrast widi theoretical band structure calculations concluding metallic behavior because of being based on incorrect idealized structures. The actual band scheme (gaps 2.09 and 2.41 eV) exhibiting high-density gap states allows consistently interpreting the experimental results. - Seebeck coefficients of -300 μV/K up to 2000 K make it a promising candidate for thermoelectric energy conversion. Theoretical speculations on superconductivity up to 36.7 K were not confirmed.
机译:碳化硼(均匀范围B_(4.3)C - B_(11)c)表现为每个基本细胞〜15个原子,由B_(12)或B_(11)C ICOSAHEDRA和线性结构元素CBC,CBB或BOB组成(□ ,空缺),其股份取决于化学成分。它们的随机分布不包括X射线衍射和NMR从结构分析中。声子纯硼碳化物上的声光谱解决了这个问题。 - 实验研究建立了半导体特征。它们对比Widi理论频带结构计算结束金属行为,因为基于不正确的理想结构。具有高密度间隙状态的实际频带方案(间隙2.09和2.41eV)允许始终如一地解释实验结果。 - 高达2000 K的塞贝克系数-300μV/ k使其成为热电能量转换的有希望的候选者。未确认高达36.7 k的超导性的理论簇。

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