Relaxation mechanisms in a benzyl chloride-toluene glass.
Relaxation mechanisms in a benzyl chloride-toluene glass.
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氯化苄-甲苯玻璃中的弛豫机制。
DOI：
10.1103/physrevb.43.9906
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Wu
中科院分区：
文献类型：
--
作者：
Wu
使用频率依赖的介电极化率，我们研究了三种不同类型的弛豫现象，即初级（\ensurmath {\alpha}），次级（\ensurmath {\beta}），和电导率（c）弛豫，在甲苯中的25体积%的氯化苄样品。测量涵盖了十年的频率：${10}^{\mathrm{-}}3}$${10}^{7}$ Hz。由于样品中的移动的离子杂质引起的电导弛豫具有与初级弛豫相似的特征。利用玻璃中初级弛豫响应的普适标度曲线，我们可以分离出频率重叠的初级弛豫和次级弛豫。二次弛豫的形状在频域中是对数正态的，并且对应于能量势垒的高斯分布。这个过程的弛豫时间可以用阿克里乌斯形式拟合。将数据外推到更高的温度，我们发现它穿过初级松弛曲线。我们比较了一组相似的分子液体，并得出结论，二次弛豫主要是由于在氯化苄分子中的一个子群的旋转。我们还报告了非线性介电响应的测量。有没有证据表明，一个发散的非线性极化率接近玻璃化转变。
Using frequency-dependent dielectric susceptibility, we have studied three different types of relaxation phenomena, namely primary (\ensuremath{\alpha}), secondary (\ensuremath{\beta}), and conductivity (c) relaxation, in a sample of 25 vol % benzyl chloride in toluene. The measurement covers ten decades of frequency: ${10}^{\mathrm{\ensuremath{-}}3}$${10}^{7}$ Hz. The conductivity relaxation which is due to mobile ionic impurities in the sample has characteristics similar to those of the primary relaxation. Using the universal scaling curve for the primary relaxation response in glasses, we can separate the primary and secondary relaxations which overlap in frequency. The shape of the secondary relaxation is log-normal in the frequency domain and corresponds to a Gaussian distribution of energy barriers. The relaxation time for this process can be fitted by an Arrhenius form. Extrapolating the data to higher temperatures, we find that it crosses the primary-relaxation curve. We compare a set of similar molecular liquids and conclude that the secondary relaxation is mainly due to the rotation of a subgroup in the benzyl chloride molecule. We also report a measurement of the nonlinear dielectric response. There is no evidence of a divergent nonlinear susceptibility as the glass transition is approached.