Phase transition behavior and proton conduction mechanism in cesium hydrogen sulfate/silica composite
Phase transition behavior and proton conduction mechanism in cesium hydrogen sulfate/silica composite
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硫酸氢铯/二氧化硅复合材料的相变行为和质子传导机制
DOI：
10.1016/j.jpcs.2004.07.006
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Hiroshi Takahashi
中科院分区：
文献类型：
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作者：
J. Otomo;H. Shigeoka;H. Nagamoto;Hiroshi Takahashi
采用拉曼光谱、XRD、差热分析等方法对多晶CsHSO4和介孔二氧化硅颗粒组成的CsHSO4/ sio2复合材料的电导率和晶体结构进行了研究。纯CsHSO4的电导率在414K（超质子相变）左右发生突变，伴随着结构从单斜相转变为四方相，而在超质子相变临界温度（353-414K）以下，CsHSO4/ sio2复合材料的电导率明显比纯CsHSO4大3个数量级以上。拉曼光谱和x射线衍射分析表明，复合材料的这种显著的电导率增强不是由于四方相（超质子相）在其临界温度以下的稳定。拉曼光谱内部模式的谱线展宽表明，在低于临界温度的情况下，HSO4−离子的快速重定向运动导致了超质子传导。当温度低于临界温度时，HSO4 -离子的重定向运动将发生在结构无序的界面相上，并在介孔和/或二氧化硅颗粒表面形成cshso4 -和sio2之间。质子的转移将通过复合材料的界面传导途径加速。
Proton conduction and crystal structure in CsHSO4/SiO2composite composed of polycrystalline CsHSO4and mesoporous silica particles were investigated based on conductivity measurement and characterizations using Raman spectroscopy, XRD, and differential thermal analysis. The conductivity of pure CsHSO4abruptly changes at around 414K (superprotonic phase transition), being accompanied with the structural transformation from a monoclinic phase to a tetragonal phase, while the conductivity of CsHSO4/SiO2composite is significantly larger by over three orders of magnitude than that of pure CsHSO4below the critical temperature of the superprotonic phase transition (353–414K). Raman spectroscopy and XRD indicate that this remarkable conductivity-enhancement in the composite is not due to the stabilization of the tetragonal phase (superprotonic phase) below its critical temperature. The line-broadening of the internal modes in the Raman spectra suggests that the rapid reorientational motion of the HSO4−ion, which leads to superprotonic conduction, is induced in the composite even below the critical temperature. The reorientational motion of the HSO4−ion below the critical temperature will occur at the interfacial phase which is structurally disordered and forms between CsHSO4and SiO2in the mesopores and/or on the surfaces of silica particles. Proton transfer will be accelerated via the interfacial conduction-pathway in the composite.