VOLUME EFFECT OR PADDLE-WHEEL MECHANISM - FAST ALKALI-METAL IONIC-CONDUCTION IN SOLIDS WITH ROTATIONALLY DISORDERED COMPLEX ANIONS
VOLUME EFFECT OR PADDLE-WHEEL MECHANISM - FAST ALKALI-METAL IONIC-CONDUCTION IN SOLIDS WITH ROTATIONALLY DISORDERED COMPLEX ANIONS
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DOI：
10.1002/anie.199115471
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发表时间：
1991-12-01
期刊：
影响因子：
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通讯作者：
JANSEN, M
中科院分区：
文献类型：
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作者：
JANSEN, M
固体中的输运现象在基础研究和实践中具有同等重要的意义。 在过去的二十年里，人们对所谓的“快”或“超”离子导体特别感兴趣，因为它们具有诱人的潜在应用。 我们已经合成了基于离子晶体的高导电性碱金属离子导体，其中，一方面，高浓度的电荷载流子可以通过掺杂（阳离子子结构中的点缺陷）来实现，另一方面，位点交换的活化能通过固定但旋转移动的络合阴离子来降低。 具有Na 3 PO 4或Na 3AlF 6结构的混合晶体已经证明在这方面特别合适。 为了建立一个更广泛的实验基础，以澄清有争议的问题，即是否较高的自由传输体积或旋转运动的阴离子是负责高阳离子的流动性，在这些旋转阶段，我们系统地改变了类型的阴离子和浓度的缺陷，并监测由此产生的电导率的变化。 虽然研究的宏观特征不适合在原子水平上详细解释机制，但结果为“桨轮机制”的假设提供了明确的支持;而且扩大的运输量的影响也是无可争议的。 这两种增强阳离子电导率的效应伴随着不同体系的量而起作用;它们不能完全彼此分开。 从这个角度来看，替代的“体积效应”或“桨轮机制”并不像前面讨论的那样明确。
Transport phenomena in the solid state are of equal importance in basic research and practice. In the past two decades particular interest has been directed towards so-called ''fast'' or ''super'' ionic conductors because of their attractive potential applications. We have synthesized highly conductive alkali-metal ionic conductors based on ionic crystals in which, on the one hand, high concentrations of the charge carriers can be realized by doping (point defects in the cation substructure) and, on the other, the activation energy of the interchange of sites is decreased by translationally fixed but rotationally mobile complex anions. Mixed crystals with Na3PO4 or Na3AlF6 structures have proven especially suitable in this connection. With the object of establishing a broader experimental foundation for clarifying the controversially discussed question of whether the higher free transport volume or the rotational motion of the anions is responsible for the high cation mobility in these rotary phases we have systematically varied the type of anions and concentration of defects and monitored the resulting changes in conductivity. Although the macroscopical characteristics investigated are not suitable for explaining mechanisms in detail at the atomic level, the results afford clear support for the assumption of a ''paddle wheel mechanism''; but also effects of the enlarged transport volume are not to be disputed. Both these effects enhancing the cationic conductivity are concomitantly operative in amounts varying from system to system; they cannot be totally separated from each other. Seen in this light, the alternative, ''volume effect'' or ''paddle wheel mechanism,'' is not as sharply defined as was previously discussed.