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Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON2.
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2020-07-10 , DOI: 10.1002/anie.202006519
Judith Oró-Solé 1 , Ignasi Fina 1 , Carlos Frontera 1 , Jaume Gàzquez 1 , Clemens Ritter 2 , Marina Cunquero 3 , Pablo Loza-Alvarez 3 , Sergio Conejeros 4 , Pere Alemany 5 , Enric Canadell 1 , Josep Fontcuberta 1 , Amparo Fuertes 1
Affiliation  

Non‐centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON2, which shows a polar 6H polytype. Synchrotron X‐ray and neutron powder diffraction, and annular bright‐field in scanning transmission electron microscopy indicate that it crystalizes in the non‐centrosymmetric space group P63mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX3 layers. A synergetic second‐order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W6+ cations, induce large distortions at two inequivalent face‐sharing octahedra that lead to long‐range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity.

中文翻译:

工程极性氧氮化物:六角形钙钛矿BaWON2。

非中心对称极性化合物具有重要的技术性能。报道的钙钛矿型氧氮化物显示出中心对称的结构,对于其中的某些,已经观察到高介电常数并将其归因于由氮化物和氧化物的偏序引起的局部偶极子。此处报道的是第一个六角形钙钛矿型氧氮化物BaWON 2,其显示极性6H多型。同步加速器X射线和中子粉末衍射以及扫描透射电子显微镜中的环形亮场表明,它在非中心对称空间群P6 3 mc中结晶,在两个不同的配位环境中,在立方晶格和立方晶中,氮化物和氧化物的总级数相同。六角包装BaX 3层。协同的二阶Jahn-Teller效应在第一原理计算,阴离子阶数和W 6+阳离子之间的静电排斥的支持下,在两个不等价的面部共享八面体处引起大畸变,导致长程有序偶极子和自发极化。 c轴。新的氮氧化物是一种带隙为1.1 eV,介电常数大的半导体。
更新日期:2020-07-10
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