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Self-Organized Transformation from Hexagonal to Orthorhombic Bronze of Cs–Nb–W–O Mixed Oxides Prepared Hydrothermally
Crystal Growth & Design ( IF 3.8 ) Pub Date : 2017-11-08 00:00:00 , DOI: 10.1021/acs.cgd.7b00999
Maria D. Soriano 1 , Ester García-González 2 , Patricia Concepción 1 , Cristiane B. Rodella 3 , Jose M. López Nieto 1
Affiliation  

The thermal transformation of hydrothermally prepared Cs–Nb–W–O mixed oxides has been studied in the 25–1000 °C temperature range. Structural evolution of the prepared solids was monitored by in situ synchrotron X-ray diffraction, absorption spectroscopy techniques, conventional powder X-ray diffraction, thermogravimetric analysis, infrared and Raman spectroscopy, and high resolution transmission electron microscopy (HRTEM and STEM). The as-grown solids show the hexagonal tungsten bronze (HTB) structure, which can be stabilized above 900 °C depending on the chemical composition. From this temperature, solids are selectively transformed into the orthorhombic Cs0.5(Nb2.5W2.5)O14 structure-type. The same results are obtained for Cs0.5(Nb2.5W2.5–xMx)O3, with M = V or Mo (x = 0–1.25). A mechanism for the quantitative transformation at high temperature is proposed in terms of the relative occupancy of the hexagonal channels in the HTB-type phase as well as the Nb/(W + V) ratio.

中文翻译:

水热法制备的Cs-Nb-W-O混合氧化物从六角形到正交晶形的自组织转变

在25–1000°C的温度范围内研究了水热制备的Cs–Nb–W–O混合氧化物的热转变。通过原位同步加速器X射线衍射,吸收光谱技术,常规粉末X射线衍射,热重分析,红外和拉曼光谱以及高分辨率透射电子显微镜(HRTEM和STEM)监测制备的固体的结构演变。刚生长的固体显示出六方钨青铜(HTB)结构,根据化学组成,该结构可以在900°C以上稳定。在此温度下,固体被选择性地转化为正交晶Cs 0.5(Nb 2.5 W 2.5)O 14结构类型。相同的结果是为获得铯0.5(NB 2.5 w ^ 2.5 X中号X)O 3,其中M = V或Mo(X = 0-1.25)。根据HTB型相中六角形通道的相对占有率以及Nb /(W + V)比,提出​​了一种高温下定量转变的机理。
更新日期:2017-11-09
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