Phase Diagrams and Functional Properties of Transition-Metal-Alloy Clusters

过渡金属合金团簇的相图和功能特性

基本信息

批准号：
11450234
负责人：
SUMIYAMA Kenji
金额：
$ 9.86万
依托单位：
Nagoya Institute of Technology (2000)Tohoku University (1999)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

In this research, we have elucidated the following points1) We have installed two sorts of metal targets in the plasma-gas-condensation cluster deposition apparatus, produced alloy clusters with 5-10 nm in diameter, and deposited on a substrate. The transmission electron microscope observation and EDX analysis indicate characteristic aspects in comparison with the equilibrium phase diagrams : (a) the compositional fluctuation is not so marked and a B2-type ordered phase is formed in Co-Al (a compound formation type), (b) the compositional fluctuation is slightly detectable and a disordered fcc phase in Co-Pt (an ordered phase formation type), (c) the compositional fluctuation is enhanced and a fcc disordered phase in Co-Pd (a homogeneous solid solution type), and (d) the compositional distribution curve has double peaks, but the primary solid solutions are formed in Nb-Ag (an immiscible type).2) Magnetization curves at 290 K as a function of the cluster size show ferromagnet-superparamagnet transition at around 8 nm in diameter.3) Co core-shell cluster assemblies, Co CSCA, prepared by slight oxidation and deposition on a substrate, show a marked tunneling type conductivity and magnetoresistance with a Coulomb-blockade effect. It also shows a crossover from a thermal type to a quantum tunneling type magnetic relaxation.4) The electrical resistivity measurement indicates that with increasing the degree of oxidation, Co, Ti and Cr CSCA changes from a metal (the temperature coefficient of resistivity, TCR, is positive) to a semiconductor (TCR is negative : an activation type), while Cu CSCA is always metallic. In the intemediate oxidation stage, TCR is positive at high temperature, while it become negative (-logT dependence) at low temperature, indicating a weak electron locarization effect. We are investigating their electronic states. These core-shell clusters will be useful for a tiny gas sensor and catalyses.

在这项研究中，我们已经阐明了以下几点1）我们已经在等离子 - 气体 - 凝结簇沉积设备中安装了两种金属靶标，并产生了直径为5-10 nm的合金簇，并沉积在底物上。透射电子显微镜观察和EDX分析表明与平衡相图相比，特征方面：（a）在CO-AL（化合物形成类型）中形成了组成波动，并形成B2型有序相位，（（ b）组成波动略有检测，并且在共同体中的FCC相位无序相位（有序相形的形成类型），（c）增强了组成波动，并在共同PD（均质实心溶液类型）中的FCC无序相位（一种均质的实心溶液类型），（d）组成分布曲线具有两倍的峰，但是主要的固体解决方案是在NB-AG中形成的（不可分用的类型）。2）在290 K处的磁化曲线作为群集尺寸的函数，显示了Ferromagnet-Superparamagnet在附近的差异。直径为8 nm。3）CO CORE-SHELL群集组件，CO CSCA，通过在基板上轻微氧化和沉积制备，显示出具有库隆阻滞作用的明显隧穿的电导率和磁性电势。它还显示了从热类型到量子隧穿型磁性松弛的交叉。4）电阻率测量表明，随着氧化程度的增加，CO，Ti和Cr CSCA随着金属的电阻率，TCR的温度系数，TCR的温度系数而变化，是阳性的）对半导体（TCR为负：激活类型），而Cu CSCA始终是金属的。在纯化的氧化阶段，TCR在高温下为正，而在低温下，TCR变为负（-logt依赖性），表明电子局部效应较弱。我们正在研究他们的电子状态。这些核心壳簇将对微小的气体传感器和催化剂有用。