Abstract The morphology evolution from monoclinic molybdenum trioxide (β-MoO3) to orthorhombic molybdenum trioxide (α-MoO3) and quantitative analyses of their mixtures were examined. It was found that the morphology (from spherical to elliptical shape) and color (from green to white) displayed obvious changes when β-MoO3 converted to α-MoO3 in ambient air at 773 K. The transformation from β-MoO3 to α-MoO3 resulted from a change of the internal crystalline structure. The mass percent of β-MoO3 in MoO3 mixtures showed an excellent linear relationship with the relative intensity ratio of the strongest peaks in X-ray diffraction patterns. This approach provides a simple and time-saving method to evaluate the amount of β-MoO3, which is a promising material in catalyst and electrochemical applications, in such mixtures. This finding may provide guidance for the analysis of catalytic performance of MoO3 mixtures. In addition, it was found that β-MoO3 can be easily decomposed into suboxides such as MoO2 and Mo4O11 in pure argon gas atmosphere. The possible decomposition mechanism of β-MoO3 is discussed.

中文翻译：

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β-MoO3 和 α-MoO3 的形貌演变和定量分析

摘要 研究了从单斜晶系三氧化钼 (β-MoO3) 到斜方晶系三氧化钼 (α-MoO3) 的形态演变及其混合物的定量分析。发现在773 K环境空气中β-MoO3转化为α-MoO3时，形貌（从球形到椭圆形）和颜色（从绿色到白色）显示出明显的变化。 从β-MoO3到α-MoO3的转化由内部晶体结构的变化引起的。MoO3 混合物中 β-MoO3 的质量百分比与 X 射线衍射图中最强峰的相对强度比显示出极好的线性关系。这种方法提供了一种简单且省时的方法来评估 β-MoO3 的含量，β-MoO3 是此类混合物中在催化剂和电化学应用中很有前景的材料。这一发现可能为分析 MoO3 混合物的催化性能提供指导。此外，发现β-MoO3在纯氩气气氛中很容易分解成低价氧化物如MoO2和Mo4O11。讨论了 β-MoO3 可能的分解机制。