Evidence of secondary relaxations in the dielectric spectra of ionic liquids
Evidence of secondary relaxations in the dielectric spectra of ionic liquids
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DOI：
10.1103/physrevb.73.212201
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发表时间：
2005-07
影响因子：
3.7
通讯作者：
A. Rivera;E. Roessler
中科院分区：
文献类型：
--
作者：
A. Rivera;E. Roessler
采用频率为10^(-6)-10^9 Hz，频率为15十年的宽带介电光谱，在400 K到35 K的温度范围内，研究了相同的1-丁基-3-甲基咪唑阳离子和不同阴离子组成的一系列室温离子液体的动力学。在玻璃化转变温度T_{g}以上观察到离子电导率与电模量表示中的弛豫。在T_{g}以下，出现了两个弛豫过程，其特征与在分子玻璃中典型观察到的二次弛豫相同。二级反应的活化能及其对阴离子的依赖性不同。较慢的过程表现出Johari-Goldstein弛豫的特征，特别是活化能E_{β}=24k_{B}T_{g}，在分子玻璃中观察到。
We investigated the dynamics of a series of room temperature ionic liquids based on the same 1-butyl-3-methyl imidazolium cation and different anions by means of broadband dielectric spectroscopy covering 15 decades in frequency (10^(-6)-10^9 Hz), and in the temperature range from 400 K down to 35 K. An ionic conductivity is observed above the glass transition temperature T_{g} with a relaxation in the electric modulus representation. Below T_{g}, two relaxation processes appear, with the same features as the secondary relaxations typically observed in molecular glasses. The activation energy of the secondary processes and their dependence on the anion are different. The slower process shows the characteristics of an intrinsic Johari-Goldstein relaxation, in particular an activation energy E_{beta}=24k_{B}T_{g} is found, as observed in molecular glasses.