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Transport and defect mechanism in copper-based delafossite materials.

机译：铜基铜铁矿材料的传输和缺陷机理。

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摘要

The defect mechanism and transport properties of cuprous-based delafossite compounds of the general form CuMO2 (M = Al, Sc, and Y) were investigated. The size of the B-site cation (M), plays a significant role in determining the electrical properties of the compound. All the systems under investigation, regardless of B-site cation, are small polaron conductors which exhibit thermally activated mobilities, consequently the upper bound of mobility is 0.10--1.0 cm2 V -1 s-1.; The defect mechanism is strongly dependant on the size and chemistry of the B-site cation. The Al-compound has a moderate room temperature conductivity of ∼1.5 x 10-2 S/cm and a hole concentration on the order of 1019 cm-3. Intrinsic defects such as Oi″ and VCu• as well as tramp impurity (e.g., CaAl') do not contribute significantly to the hole population, which corresponds to approximately 1% polaron occupation of the Cu sites at high temperatures. A defect associate of the form (AlCu••2O i″)″ was found to be the dominant source of hole generation in CuAlO2. At low temperatures two holes (CuCu•) tightly bind with forming a neutral complex.; The large B-site cation compounds (CuScO2 and CuYO2) do not exhibit an equivalent defect associate due to the instability of Sc and Y in low coordination sites, therefore the intrinsic Sc- and Y-compounds have inferior electrical properties compared to CuAlO2. The large B-site compounds do, however, have a propensity for acceptor dopants, e.g., oxygen interstitials and extrinsic doping. Under the experimental conditions of this study, isolated oxygen interstitials were found in insignificant concentrations. The solubility limits of Mg in CuScO2 and Ca in CuYO2 were found to be approximately 1% and 0.2%, respectively, corresponding to room temperature conductivities of 2 x 10-2 and 1.7 x 10-3 S cm-1---substantial increases from the undoped values. Based on small polaron theory a maximum conductivity was determined to be ∼600 S cm-1 for the delafossite materials.; A technique, utilizing impedance spectroscopy and effective medium theory, was also established to measure the conductivity of ceramic powders in order to make comparisons between the solid-state synthesized and hydrothermally prepared CuAlO2, which has been shown to have an order of magnitude greater conductivity due to an increase in (AlCu•• 2Oi″)″.
机译：研究了一般形式为CuMO2（M = Al，Sc和Y）的基于亚铜的铜铁矿化合物的缺陷机理和传输性能。 B位阳离子（M）的大小在确定化合物的电学性质方面起着重要作用。所研究的所有系统，无论B位阳离子如何，都是具有热活化迁移率的小型极化子导体，因此迁移率的上限为0.10--1.0 cm2 V -1 s-1。缺陷机理在很大程度上取决于B位阳离子的大小和化学性质。铝化合物的室温电导率约为1.5 x 10-2 S / cm，空穴浓度约为1019 cm-3。诸如Oi''和VCu•之类的固有缺陷以及杂质（例如，CaAl'）对空穴总数的贡献不大，这对应于高温下Cu位置的极化子占有率约为1％。发现（AlCu••2O i''）''形式的缺陷缔合体是CuAlO2中产生空穴的主要来源。在低温下，两个孔（CuCu•）紧密结合，形成中性络合物。由于Sc和Y在低配位位置的不稳定性，大的B位阳离子化合物（CuScO2和CuYO2）没有表现出等效的缺陷缔合，因此与CuAlO2相比，固有的Sc和Y化合物的电性能较差。但是，大的B位化合物确实具有受主掺杂剂的倾向，例如氧间隙和非本征掺杂。在这项研究的实验条件下，孤立的氧间隙被发现微不足道的浓度。发现Mg在CuScO2中的溶解度极限和Ca在CuYO2中的溶解度极限分别约为1％和0.2％，对应于室温电导率2 x 10-2和1.7 x 10-3 S cm-1--大幅增加从未掺杂的值。根据小极化子理论，对于铜铁矿材料，最大电导率确定为〜600 S cm-1。还建立了一种利用阻抗光谱学和有效介质理论的技术来测量陶瓷粉末的电导率，以便在固态合成和水热制备的CuAlO2之间进行比较，这已显示出由于电导率更高而增加了一个数量级。 （AlCu••2Oi''）''的增加。

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  • 作者

    Ingram, Brian James.;

  • 作者单位

    Northwestern University.;

  • 授予单位 Northwestern University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 178 p.
  • 总页数 178
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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