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首页> 外文期刊>Journal of Materials Chemistry, A. Materials for energy and sustainability >Co3O4 nanostructures: the effect of synthesis conditions on particles size, magnetism and transport properties
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Co3O4 nanostructures: the effect of synthesis conditions on particles size, magnetism and transport properties

机译：CO3O4纳米结构：合成条件对粒子尺寸，磁性和运输性能的影响

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Surfactant-free Co3O4 nanostructures with various particle size ranges were synthesized via the solution combustion method using cobalt nitrate solution as a cobalt precursor and urea as a combustion fuel. Control over average particles size range was achieved by tuning the reaction ignition temperature between 300 °C and 800 °C. X-ray diffraction (XRD) and helium gas pycnometry indicated the formation of single phase Co3O4 nanopartlcles with a spinel structure. Transmission electron microscopy (TEM) studies revealed an Increase of the size range from 5-8 nm to 200-400 nm for Co3O4 nanopartlcles synthesized at 300 °C and 800 °C, respectively The corresponding decrease in the specific surface area from 39 m~2 g~(-1) to ~2 m~2 g~(-1) was confirmed by gas adsorption analysis using BET techniques. Magnetic susceptibility measurements revealed a dominant antiferromagnetic (AFM) ordering and the Neel temperature decreases with a decreasing average particle size range from 31 K (200-400 nm) to 25 K (5-18 nm). Interestingly, effective magnetic moments (ranging from 4,12 μ_B to 6.16 μ_B) substantially larger than the value of 3.9 μ_B expected for Co~(2+) ions in the normal spinel structure of Co3O4 were extracted from the inverse susceptibility data. This finding was rationalized by taking into account the disordered distribution of Co~(2+) and Co~(3+) ions in the Co3O4 inverse spinel structures ([(Co~(2+))_(1-cx)(Co~(3+))_x]~(tet)[(Co~(2+))_xCo~(3+))_(2-x)]_(oct)O4) where the inversion degree (x) depends on the synthesis temperature. Transport measurements using hot pressed pellets of Co3O4 nanopartlcles indicated p-type semiconducting behavior and drastic reductions in the thermal conductivity with decreasing average particle size.
机译：通过使用钴硝酸溶液作为钴前体和尿素作为燃烧燃料，通过溶液燃烧方法合成具有各种粒度范围的无表面活性剂CO3O4纳米结构。通过在300℃和800℃之间调节反应点火温度来实现平均粒子尺寸范围的控制。 X射线衍射（XRD）和氦气Pycnometry表示用尖晶石结构形成单相CO3O4纳米颗粒。透射电子显微镜（TEM）研究表明，在300℃和800℃合成的CO3O4纳米颗粒的尺寸范围内的尺寸范围增加，分别从39m〜的比表面积相应的降低使用BET技术通过气体吸附分析确认2g〜（-1）至约2m〜2g〜（-1）。磁化率测量揭示了主要的反铁磁性（AFM）排序，并且NEER温度随着31k（200-400nm）至25k（5-18nm）的平均粒度的降低范围而降低。有趣的是，从逆敏感性数据中提取有趣的磁矩（范围为4,12μg至6.16μm）基本上大于CO 3 O4的正常尖晶石结构中的CO〜（2+）离子的3.9μg％的值。通过考虑Co3O4反尖晶石结构中的CO〜（2+）和CO〜（3+）离子的无序分布（[（CO〜（2 +））_（1-CX）（CO 〜（3 +））_ x]〜（tet）[（Co〜（2 +））_ xco〜（3 +））_（2-x）] _（10-x））_（oct）o4），其中反转程度（x）取决于合成温度。使用Co3O4纳米粒子的热压粒料的运输测量指示p型半导体行为，并且随着平均粒度的降低，导热率的激烈减少。

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    Pranati Sahoo; Honore Djieutedjeu; Pierre F. P. Poudeu;

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    Laboratory for Emerging Energy and Electronic Materials Department of Materials Science and Engineering University of Michigan Ann Arbor MI 48109 USA.;

    Laboratory for Emerging Energy and Electronic Materials Department of Materials Science and Engineering University of Michigan Ann Arbor MI 48109 USA.;

    Laboratory for Emerging Energy and Electronic Materials Department of Materials Science and Engineering University of Michigan Ann Arbor MI 48109 USA.;

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