Anisotropic Crystal Growth of Layered Vanadates with Bulky Interlayer Cations
Anisotropic Crystal Growth of Layered Vanadates with Bulky Interlayer Cations
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DOI：
10.1002/crat.202200198
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发表时间：
2023-01
影响因子：
1.5
通讯作者：
T. Ban;Karin Konishi;Motoki Mizuno;Chika Takai-Yamashita;Y. Ohya
中科院分区：
文献类型：
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作者：
T. Ban;Karin Konishi;Motoki Mizuno;Chika Takai-Yamashita;Y. Ohya
研究了同时含有V4+和V5+的层状四甲基八钒酸铵[N（CH 3）4] V8 O20在水热合成过程中的晶化行为。根据Bravais-Friedel-Donnay-Harker定律，具有大体积层间阳离子的层状金属化物晶体倾向于具有平行于金属化物层的大表面的形状;然而，在结晶的早期阶段产生沿垂直于钒酸盐层的方向沿着伸长的小棒状晶体。随着结晶的进行，晶体形状变成大的带状和片状，其最大表面平行于钒酸盐层。如果溶胶中只含有在结晶早期形成的小棒状晶体，它们将是有用的钒酸盐层垂直对齐垂直于衬底表面的薄膜的制造。此外，[N（CH 3）4] V8 O20晶体的水性悬浮液的超声处理导致其剥落至几十纳米的厚度。由于晶体形状与晶体学方向的关系，超声波处理得到的小晶体与晶化初期形成的小晶体不同。在结晶早期形成的小棒状晶体的形貌可能是亚稳态生长形式的结果。
The crystallization behavior of layered tetramethylammonium octavanadate [N(CH3)4]V8O20 including both V4+ and V5+ during hydrothermal synthesis is examined. According to the Bravais–Friedel–Donnay–Harker law, layered metalate crystals with bulky interlayer cations tend to have shapes with large surfaces parallel to the metalate layers; however, small rodlike crystals elongated along the direction normal to the vanadate layers are produced at the early stage of crystallization. As the crystallization proceeds, the crystal shapes are changed to large belt‐like and platelike ones with the largest surfaces parallel to the vanadate layers. If sols containing only the small rodlike crystals formed at the early stage of crystallization are prepared, they will be useful for the fabrication of thin films with the vanadate layers vertically aligned normal to the substrate surface. Furthermore, ultrasonic treatment of the aqueous suspensions of the [N(CH3)4]V8O20 crystals leads to their exfoliation to a thickness of several tens of nanometers. For the relation between crystal shapes and crystallographic directions, the small crystals obtained using ultrasonic treatment are different from the ones formed at the early stage of crystallization. Probably, the morphology of the small rodlike crystals formed at the early stage of crystallization is attributed to the metastable growth form.