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首页> 外文期刊>Crystal growth & design >Assembled synthesis and phase transition of pseudovaterite NdBO3 layer-by-layer single-crystal nanopancakes via an oxides-hydrothermal route
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Assembled synthesis and phase transition of pseudovaterite NdBO3 layer-by-layer single-crystal nanopancakes via an oxides-hydrothermal route

机译：伪球体NdBO3层状单晶纳米薄饼的氧化物-水热法合成与相变

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A neotype NdBO3 crystal structure and its layer-by-layer nanopancakes are first obtained by mixing Nd2O3 and B2O3 in stoichiometric amounts without any additive via a mild oxides-hydrothermal (O-HT) process. Characterizations of the samples are carried out using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), and electron diffraction (ED). The pseudovaterite hexagonal structure is tentatively identified by XRD and FTIR. Typical nanopancakes are uniform nanosheets with a layer-by-layer self-assembled single-crystal structure. The thickness of each layer is about 50 nm, and the diameter is up to 14 mu m. The influences of treatment time, synthesis temperature, filling ratio, and pH value of solution on products are investigated. The results show that the formation processes of NdBO3 in the O-HT system can be assigned to two stages: M2O3 (M = Nd, B) oxides transformed into hydroxide, M(OH)(3), and the products formed by the interaction between hydroxides. Both heat-treatment time and temperature are favorable for crystal growth, but pancake-like nanostructures are destroyed beyond the appropriate conditions. Hexagonal phase NdBO3 crystals can only be obtained in a narrow pH region (5 <= pH < 7). The formation mechanism of pseudovaterite NdBO3 is discussed. The thermal stability and irreversible phase transition properties of pseudovaterite NdBO3 crystal are studied and confirmed.
机译：一种新型的NdBO3晶体结构及其逐层纳米煎饼首先是通过温和的氧化物-水热（O-HT）工艺将化学计量的Nd2O3和B2O3混合而没有任何添加剂而获得的。使用X射线粉末衍射（XRD），傅立叶变换红外光谱（FTIR），扫描电子显微镜（SEM），透射电子显微镜（TEM）和高分辨率TEM（HRTEM）以及电子衍射对样品进行表征（ED）。用XRD和FTIR初步确定了伪球晶的六边形结构。典型的纳米薄饼是具有逐层自组装单晶结构的均匀纳米片。每层的厚度约为50nm，直径最大为14μm。研究了处理时间，合成温度，填充比和溶液pH值对产物的影响。结果表明，O-HT系统中NdBO3的形成过程可分为两个阶段：氧化成氢氧化物的M2O3（M = Nd，B）氧化物，M（OH）（3）和相互作用形成的产物在氢氧化物之间。热处理时间和温度都有利于晶体生长，但是在适当的条件下，煎饼状的纳米结构会被破坏。六方相NdBO3晶体只能在狭窄的pH区域（5 <= pH <7）中获得。讨论了伪球NNdBO3的形成机理。研究并证实了伪球ate石NdBO3晶体的热稳定性和不可逆相变特性。

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