Temperature Dependence of the Static Relative Permittivity of Octylcyanobiphenyl (8CB)
Temperature Dependence of the Static Relative Permittivity of Octylcyanobiphenyl (8CB)
复制标题
辛基氰基联苯 (8CB) 静态相对介电常数的温度依赖性
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
G. Menu
中科院分区：
文献类型：
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作者：
J. Thoen;G. Menu
本文报道了辛基氰基联苯（8 CB）在22°C ~ 140°C范围内近晶A相、近晶B相和各向同性相的相对静态介电常数ε的测量结果。测量分辨率优于0.01%，温度稳定性优于0.01 °C。在AN和NI转变附近进行了详细的测量。为了转型。e无间断||或e|观察到，这是符合的二阶性质的这种转变在8 CB。从N相的介电各向异性出发，得到了序参量随温度变化的临界指数β = 0.25。这个β值支持了这个转变的准三临界性假设。在各向同性相的8 CB，在过渡前的异常最大值e附近观察到的TN 1。同样的效果也测量了其他两种材料与氰基端基（十一烷基氰基联苯和戊基氰基苯基环己烷）。对于两种没有氰基末端基团的化合物，
Abstract Measurements of the relative static permittivity e of octylcyanobiphenyl (8CB) in the smectic A, the nematic and the isotropic phases between 22°C and 140°C are reported. The resolution of the measurements was better than 0.01% and the temperature stability was better than 0.01 °C. Detailed measurements have been carried out near the AN and NI transitions. For the AN transition. no discontinuity in e|| or e| was observed, which is consistent with the second-order nature of this transition in 8CB. From the dielectric anisotropy in the N-phase, a critical exponent β ≃ 0.25 was obtained for the temperature dependence of the order parameter. This value of β is in support of the hypothesis of quasi-tricriticality for this transition. In the isotropic phase of 8CB, a pretransitional anomalous maximum in e was observed near T N1- The same effect was also measured for two other materials with cyano-end groups (undecylcyanobiphenyl and pentylcyanophenylcyclohexane). For two compounds without a cyano-end g...