FAST IONIC-CONDUCTION IN NA2S+B2S3 GLASSES - COMPOSITIONAL CONTRIBUTIONS TO NONEXPONENTIALITY IN CONDUCTIVITY RELAXATION IN THE EXTREME LOW-ALKALI-METAL LIMIT
FAST IONIC-CONDUCTION IN NA2S+B2S3 GLASSES - COMPOSITIONAL CONTRIBUTIONS TO NONEXPONENTIALITY IN CONDUCTIVITY RELAXATION IN THE EXTREME LOW-ALKALI-METAL LIMIT
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DOI：
10.1103/physrevb.45.10292
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发表时间：
1992-05-01
影响因子：
3.7
通讯作者：
MARTIN, SW
中科院分区：
文献类型：
--
作者：
PATEL, HK;MARTIN, SW
玻璃态和晶态离子导体的电导弛豫现象多年来一直被认为是一个高度非指数的过程。拉伸指数函数exp-（t/tau）beta已被不同程度地成功用于描述这种弛豫。非指数性是否是由于平行的传导过程相互独立地起作用并具有弛豫时间的分布，或者是由于串联过程强烈耦合离子传导物质并约束彼此的弛豫，该过程的确切性质仍然未知。如果耦合是导致非指数性的主动机制，那么非指数性的程度和平均离子分离距离之间应该存在关系;离子-离子分离越大，离子之间的耦合越小。为了验证这一假设，宽的组成，频率和温度范围内的电导率测量已进行的快速离子导电玻璃系列，Na 2S + B2 S3。当x（Na ~ 2S）= 0.001时，弛豫近似为指数型。随着Na 2S浓度的增加，估计的离子-离子分离距离减小;直流电导率活化能和拉伸指数中的β参数也减小。然而，β参数显示出对离子-离子分离距离的更强的依赖性。它还发现，对于几乎所有的玻璃研究到目前为止，β参数的组成依赖性可以投到一个主图的β与平均离子-离子分离距离。通过这种方式，我们提供了一个普遍的趋势，在玻璃的非指数性的组成依赖。
The conductivity relaxation phenomenon in glassy and crystalline ionic conductors has been known for many years to be a highly nonexponential process. The stretched exponential function exp-(t/tau)beta has been used with varying levels of success to describe this relaxation. Whether the nonexponentiality is due to parallel conducting processes acting independently of each other and having a distribution of relaxation times or to serial processes strongly coupling the ionically conducting species and constraining each other's relaxation, the exact nature of this process is still unknown. If coupling is the active mechanism responsible for the nonexponentiality, then there should be a relationship between the extent of the nonexponentiality and the average ion separation distance; the greater the ion-ion separation, the smaller the coupling between the ions. To test this hypothesis, wide composition, frequency, and temperature range conductivity measurements have been performed on the fast-ion-conducting glass series, Na2S + B2S3. For x(Na2S) = 0.001, the relaxation is nearly exponential. As the Na2S concentration increases, the estimated ion-ion separation distance decreases; so do both the dc conductivity activation energy and the beta-parameter in the stretched exponential. The beta-parameter, however, shows a much stronger dependence to the ion-ion separation distance. It is also found that for nearly all of the glasses studied to date, the composition dependencies of the beta-parameter can be cast onto a master plot of beta versus average ion-ion separation distance. In this way, we provide a universal trend for the compositional dependence of the nonexponentiality in glass.