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首页> 外文期刊>Crystal growth & design >Hydrothermally Synthesized h-MoO3 and alpha-MoO3 Nanocrystals: New Findings on Crystal-Structure-Dependent Charge Transport
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Hydrothermally Synthesized h-MoO3 and alpha-MoO3 Nanocrystals: New Findings on Crystal-Structure-Dependent Charge Transport

机译：水热合成h-MoO3和α-MoO3纳米晶体：依赖于晶体结构的电荷传输的新发现

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摘要

The charge transfer characteristics of metastable phase hexagonal molybdenum oxide (h-MoO3) and stable-phase orthorhombic MoO3 (alpha-MoO3) nanocrystals have been investigated for the first time using impedance spectroscopy. The results imply that the metastable phase h-MoO3 displays a 550-fold increase (at 150 degrees C) in the electrical conductivity relative to the stable phase alpha-MoO3. The conductivity also increases as the temperature increases from 130 to 170 degrees C, whereby analysis shows a thermal activation energy (E-a) of similar to 0.42 eV. The investigation clearly identifies that the presence of intercalated ammonium ions (NH4+) and crystal water molecules (H2O) in the internal structure of h-MoO3 plays a vital role in enhancing the charge transfer characteristics and showing an ionic conductive nature. Before the impedance investigations, the h-MoO3 and alpha-MoO3 nanocrystals were successfully synthesized through a wet-chemical process. Here, a controlled one-step hydrothermal route was adopted to synthesize stable-phase alpha-MoO3 nanocrystals sequentially from metastable-phase h-MoO3 nanocrystals. The hydrothermal reaction conditions, such as the choice of precipitant, amount of precipitant, reactant solvent medium, reaction time, and reaction temperature, play significant roles in defining the crystal structure, crystallite size, and particle morphology. On the basis of the crystal structure, size, and morphology evolution with respect to the hydrothermal reaction conditions, a possible formation mechanism of MoO3 nanocrystals is proposed.
机译：首次使用阻抗谱研究了亚稳相六角形氧化钼（h-MoO3）和稳定相正交晶MoO3（α-MoO3）纳米晶体的电荷转移特性。结果表明，相对于稳定相α-MoO3，亚稳定相h-MoO3在电导率上显示出550倍的增加（在150摄氏度时）。电导率也随温度从130摄氏度增加到170摄氏度而增加，因此分析表明热活化能（E-a）接近0.42 eV。研究清楚地表明，h-MoO3的内部结构中存在铵离子（NH4 +）和结晶水分子（H2O）在增强电荷转移特性和显示离子导电性方面起着至关重要的作用。在进行阻抗研究之前，通过湿化学工艺成功地合成了h-MoO3和α-MoO3纳米晶体。在此，采用受控的一步式水热法从亚稳态的h-MoO3纳米晶体依次合成稳定相的α-MoO3纳米晶体。水热反应条件，例如沉淀剂的选择，沉淀剂的量，反应剂溶剂介质，反应时间和反应温度，在确定晶体结构，微晶尺寸和颗粒形态方面起着重要作用。根据水热反应条件下的晶体结构，尺寸和形貌演变，提出了可能的MoO3纳米晶体形成机理。

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