乙铵铋基有机-无机杂化材料中的铁电：（C2H5NH3）2 [BiBr5]。,Inorganic Chemistry

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乙铵铋基有机-无机杂化材料中的铁电：（C2H5NH3）2 [BiBr5]。
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2019-12-27 , DOI: 10.1021/acs.inorgchem.9b03193
Ryszard Jakubas ₁ , Anna Ga Gor ₂ , Maciej J Winiarski ₂ , Maciej Ptak ₂ , Anna Piecha-Bisiorek ₁ , Agnieszka Ciżman ₃

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（C2H5NH3）2 [BiBr5]（EBB）晶体采用一维（1D）聚合阴离子形式[BiBr5]∞2-，这对于具有极性性质并通过R2MX5化学计量实现的卤化铋盐（III）来说是优选的。差示扫描量热法和膨胀测量法揭示了可逆的结构相变：在160 K（I相→II相）和120 K（II相→III相）下。EBB的已解析晶体结构在I相（Aeam）中显示出中心对称的空间基团，II相中显示出极性（Pca21），而III期显示出极性（Aea2）。在相II和相III中存在介电磁滞回线，这证明了铁电特性。接近160 K的EBB的介电响应[ε*（ω，T）]是具有临界减慢过程的铁电体的特征。在160 K时顺电-铁电相变的分子机理被解释为“有序-无序”（分配给乙基铵阳离子的动力学）和占主导地位的“置换”（与1D阴离子网络的强烈畸变有关）。从紫外可见测量获得的光学带隙约为2.6 eV。导带最小值由杂化的Bi 6p和Br 4p状态形成。给出了以[MX4]-，[M2X9] 3-，[MX5] 2-和[M2X11] 5-阴离子为特征的卤化锑酸盐（III）和卤化铋酸盐（III）铁电材料CSD结果的分析。导带最小值由杂化的Bi 6p和Br 4p状态形成。给出了以[MX4]-，[M2X9] 3-，[MX5] 2-和[M2X11] 5-阴离子为特征的卤化锑酸盐（III）和卤化铋酸盐（III）铁电材料CSD结果的分析。导带最小值由杂化的Bi 6p和Br 4p状态形成。给出了以[MX4]-，[M2X9] 3-，[MX5] 2-和[M2X11] 5-阴离子为特征的卤化锑酸盐（III）和卤化铋酸盐（III）铁电材料CSD结果的分析。

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Ferroelectricity in Ethylammonium Bismuth-Based Organic-Inorganic Hybrid: (C2H5NH3)2[BiBr5].

The (C2H5NH3)2[BiBr5] (EBB) crystals adopt the one-dimensional (1D) polymeric anionic form [BiBr5]∞2-, which is preferred by halobismuthates(III) exhibiting polar properties and realized in R2MX5 stoichiometry. Differential scanning calorimetry and dilatometric measurements reveal reversible structural phase transitions: at 160 K (phase I → phase II) and 120 K (phase II → phase III). The resolved crystal structures of EBB show the centrosymmetric space group in phase I (Aeam), polar (Pca21) in phase II, and polar (Aea2) in phase III. The presence of dielectric hysteresis loops in phases II and III evidence ferroelectric properties. The dielectric response [ε*(ω,T)] of EBB close to 160 K is characteristic of ferroelectrics with a critical slowing down process. The molecular mechanism of a paraelectric-ferroelectric phase transition at 160 K is explained as "order-disorder" (assigned to the dynamics of the ethylammonium cations) and dominating "displacive" (related to strong distortion of the 1D anionic network). The optical band gap obtained from UV-vis measurements is about 2.6 eV. The conduction band minimum is formed by the hybridized Bi 6p and Br 4p states. An analysis of the CSD results for haloantimonates(III) and halobismuthates(III) ferroelectrics characterized by [MX4]-, [M2X9]3-, [MX5]2-, and [M2X11]5- anions is given.

更新日期：2019-12-27

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