[(C2H5)4N][FeBrCl3] 和 [(CH3)4N][FeBrCl3] 铁质塑料晶体的中间相转变,Chemistry of Materials

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[(C2H5)4N][FeBrCl3] 和 [(CH3)4N][FeBrCl3] 铁质塑料晶体的中间相转变
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-03-09 , DOI: 10.1021/acs.chemmater.1c03778
Julian Walker ₁ , Kenneth P. Marshall _{1,

2} , Jorge Salgado-Beceiro ₃ , Benjamin A. D. Williamson ₁ , Nora S. Løndal ₁ , Socorro Castro-Garcia ₃ , Manuel Sánchez Andújar ₃ , Sverre M. Selbach ₁ , Dmitry Chernyshov ₂ , Mari-Ann Einarsrud ₁

Affiliation

塑料晶体是超分子材料，在高温下具有独特的高熵中间相，其中长程结构对称性与局部分子取向无序共存。向中间相的转变可能涉及对热能存储有用的大熵变化，并影响铁电和压电特性的温度范围，这对于传感器应用很重要。采用同步辐射X射线衍射和对分布函数分析对其结构进行研究，同时采用量热法、介电常数、漏电流测量和密度泛函理论研究有机阳离子对溴三氯铁酸四乙基铵(III)结构和性能的影响。 ) [(C ₂ H ₅ ) ₄N][FeBrCl ₃ ] 和四甲基溴化三氯铁酸铵 [(CH ₃ ) ₄ N][FeBrCl ₃ ]。[(C ₂ H ₅ ) ₄ N][FeBrCl ₃ ]中间相转变的熵变为151.5 J·K ^–1 ·kg ^–1，而[(CH ₃ ) ₄ N][FeBrCl ₃ ]只有49 J ·K ^–1 ·kg ^–1 . 这由[(C ₂ H ₅ ) ₄ N][FeBrCl ₃_{]与[(CH 3} ) ₄ N][FeBrCl ₃ ]相比，阳离子和阴离子的中间相具有较少的长程结构对称性和较多的局部取向无序。两种材料在过渡之下都表现出至少两种导电机制，即空位介导的离子和电子传导。与阳离子取向自由相反，在中间相转变处引入阴离子取向自由度对电性能影响最大。

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Mesophase Transitions in [(C2H5)4N][FeBrCl3] and [(CH3)4N][FeBrCl3] Ferroic Plastic Crystals

Plastic crystals are supramolecular materials that possess a unique high entropy mesophase at elevated temperatures, where a long-range structural symmetry coexists with a local molecular orientational disorder. The transition to mesophase can involve a large entropy change useful for thermal energy storage and influences the temperature range of ferroelectric and piezoelectric properties, important for sensor applications. Synchrotron X-ray diffraction and pair distribution function analysis were used to study the structure, while calorimetry, dielectric, leakage current measurements, and density functional theory were used to investigate the influence of the organic cation on the structure and properties of tetraethylammonium bromotrichloroferrate(III) [(C₂H₅)₄N][FeBrCl₃] and tetramethylammonium bromotrichloroferrate [(CH₃)₄N][FeBrCl₃]. The [(C₂H₅)₄N][FeBrCl₃] mesophase transition had an entropy change of 151.5 J·K^–1·kg^–1, while [(CH₃)₄N][FeBrCl₃] had only 49 J·K^–1·kg^–1. This was explained by the [(C₂H₅)₄N][FeBrCl₃] mesophase having less long-range structural symmetry and more local orientational disorder, of both the cations and anions, compared to [(CH₃)₄N][FeBrCl₃]. Both materials exhibited at least two conductive mechanisms below the transition, vacancy-mediated ionic and electronic conduction. The introduction of anion orientational freedom, as opposed to cation orientational freedom, at the mesophase transition was most influential for the electrical properties.

更新日期：2022-03-09

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