Boron doped diamond are potential superhard materials with good electric conductivity. In this work, polycrystalline boron doped diamond (p-BDD) with different boron concentration were synthesized from the mixture of graphite and boron carbide under ultra-high pressure (15 GPa) and temperature (2500-2700 K). The results indicate that no more boron atoms can be inserted into diamond when the boron concentration is above 4 at.%. The EELS spectra indicated that the boron atoms have been doped into the diamond grains, and surplus boron carbide locate at the grain boundary. The hardness measurements reveal that the p-BDD doped with 1 at.% and 23 at.% boron atoms exhibit high hardness of 78.5 GPa and 45 GPa, respectively, which is equivalent to the hardness of single crystal diamond and cubic boron nitride. The p-BDD is a semiconductor and transforms into superconductive state below 2.5 K. According to microstructure measurements, highly dense p-BDD and B₄C bonded diamond exhibit superhard behavior because of the strong bonding of diamond grains by B₄C additives. The oxidation temperature of these p-BDD specimens is around 1538 K in the air, which is far higher than diamond. B₄C is demonstrated as a superior additive to sinter superhard and electric conductive p-BDD, which are extremely useful in areas where high hardness and electric conductive are highly desired.

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中文翻译：

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不同浓度B4C合成超硬超导多晶掺硼金刚石

掺硼金刚石是具有良好导电性的潜在超硬材料。在这项工作中，在超高压 (15  GPa) 和温度 (2500-2700  K) 下，由石墨和碳化硼的混合物合成了具有不同硼浓度的多晶硼掺杂金刚石 (p-BDD)。结果表明，当硼浓度高于 4 at.% 时，无法将更多的硼原子插入金刚石中 。EELS 光谱表明硼原子已掺杂到金刚石晶粒中，多余的碳化硼位于晶界。硬度测量表明，掺杂 1  at.% 和 23 at.% 硼原子的 p-BDD 表现出 78.5 GPa 和 45 GPa 的高硬度  GPa，分别相当于单晶金刚石和立方氮化硼的硬度。p-BDD 是一种半导体，在 2.5  K 以下转变为超导状态。根据微观结构测量，高密度 p-BDD 和 B ₄ C 键合金刚石表现出超硬行为，这是因为 B ₄ C 添加剂对金刚石晶粒的强键合。这些 p-BDD 样品在空气中的氧化温度约为 1538  K，远高于金刚石。B ₄ C 被证明是烧结超硬和导电 p-BDD 的优质添加剂，在高度需要高硬度和导电性的领域非常有用。

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