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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Semimetallic paramagnetic nano-Bi_2Ir and superconducting ferromagnetic nano-Bi_3Ni by microwave-assisted synthesis and room temperature pseudomorphosis
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Semimetallic paramagnetic nano-Bi_2Ir and superconducting ferromagnetic nano-Bi_3Ni by microwave-assisted synthesis and room temperature pseudomorphosis

机译：微波辅助合成和室温拟态半金属顺磁性纳米Bi_2Ir和超导铁磁性纳米Bi_3Ni

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摘要

Uniform nanocrystals of the intermetallic compounds Bi_2Ir (diameter ' 50 nm) and Bi_3Ni (typical size 200×600 nm) were obtained by a microwave-assisted polyol process at 240 °C. The method was also applied to the spatially confined reaction environment in the microporous exo-template SBA-15 resulting in Bi_3Ni particles of about 6 nm. Non-crystalline bundles of parallel Bi_3Ni nanofibres that have an individual diameter of less than 1 nm were obtained by reductive pseudomorphosis of the subiodide Bi12Ni4I3 at room temperature. Magnetic susceptibility measurements demonstrate coexistence of ferromagnetism and superconductivity in a single phase for the nanostructured Bi_3Ni materials. Curie temperature, coercive field, remnant magnetization, saturation moment, diamagnetic screening, and critical field vary with particle size. The crystal structure of Bi_2Ir was determined by Rietveld refinement of powder X-ray diffraction data. Bi_2Ir crystallizes in the monoclinic arsenopyrite type (space group P21/c), a superstructure of the markasite type, with a = 690.11(1), b = 678.85(1), c = 696.17(1) pm, and β = 116.454(1)°. In contrast to most of the other phases of this type, the Bi_2Ir is not a diamagnetic semiconductor but a weakly paramagnetic semimetal. Conductivity measurements down to 4 K and magnetization measurements in a field of μ0H = 10mT down to 1.8 K give no evidence for a transition into the superconducting state. Bonding analysis shows prevailing contribution of Bi-Bi interactions to the conduction, whereas Bi-Ir bonding is mostly covalent and localized.
机译：金属间化合物Bi_2Ir（直径为50 nm）和Bi_3Ni（典型尺寸为200×600 nm）的均匀纳米晶体是通过微波辅助多元醇工艺在240°C下获得的。该方法还适用于微孔外模板SBA-15中的空间受限反应环境，产生约6 nm的Bi_3Ni粒子。通过在室温下对亚碘化物Bi12Ni4I3进行还原假型化，获得了单根直径小于1 nm的平行Bi_3Ni纳米纤维的非结晶束。磁化率测量结果表明，纳米结构的Bi_3Ni材料在单相中铁磁性和超导性共存。居里温度，矫顽场，剩余磁化强度，饱和矩，抗磁屏蔽和临界场随颗粒大小而变化。 Bi_2Ir的晶体结构通过粉末X射线衍射数据的Rietveld精制确定。 Bi_2Ir结晶为单斜砷黄铁矿型（空间群P21 / c），为镁铁矿型的上层结构，a = 690.11（1），b = 678.85（1），c = 696.17（1）pm和β= 116.454（ 1）°。与大多数此类其他相相比，Bi_2Ir不是抗磁性半导体，而是弱顺磁性半金属。低至4 K的电导率测量值和低至1.8 K的μ0H= 10mT磁场的磁化强度测量值均未提供过渡至超导状态的证据。键合分析显示Bi-Bi相互作用对传导的主要贡献，而Bi-Ir键则大多为共价键和局部键合。

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