柠檬酸溶胶法制备Bi2WO6粉体及其表征

利用钨酸铵、硝酸铋、柠檬酸和硝酸为原料，柠檬酸溶胶法制备了Bi₂WO₆粉体.热重-差热（TG-DTA）和红外光谱（FT-IR）分析Bi₂WO₆前驱体的热分解过程，X射线衍射（XRD）、场发射扫描电镜（FE-SEM）对Bi₂WO₆粉体结构、形貌进行表征.结果表明，Bi₂WO₆前驱体热分解分为4个阶段，其中Bi₂WO₆粉体开始形成发生在367 ℃. Bi₂WO₆前驱体在400~700 ℃煅烧5 h获得了单一的Bi₂WO₆粉体，当温度低于600 ℃时，产物为球形颗粒，晶粒尺寸随温度升高变化不大，当温度达到700 ℃时，晶粒迅速长大，最终发展成为规则的正交晶系.这表明晶体生长过程发生了由扩散机制向界面反应控制机制的转变，因此通过调整煅烧反应温度和保温时间可以控制产物的尺寸和形貌. 

Preparation and characteristics of Bi2WO6 powders by citrate sol process

Bismuth tungsten oxide (Bi₂WO₆) powders were synthesized by citrate sol process using ammonium tungstate, bismuth nitrate, citrate and nitric acid as the starting materials. The structure and morphology of as-synthesized Bi₂WO₆ samples were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM). Thermogravimetry and differential thermal analysis (TG-DTA) and Fourier transform infrared spectroscopy (FT-IR) were applied to analyze the thermal behavior of the Bi₂WO₆ precursor. There are four stages were found in the TG-DTA curves of the Bi₂WO₆ precursor, and the Bi₂WO₆ started to be formed at 367 ℃ in the third stage. The pure bismuth tungsten oxide powders were prepared by calcination of the precursors at 400~700 ℃ for 5 h. The spherical particle size of Bi₂WO₆ powders does not change apparently with increasing temperature below 600 ℃. The grain grow up rapidly and orthogonal crystal system obtained when the temperature at above 700 ℃. The crystal grow process of Bi₂WO₆ undergoes a transition from a diffusion control mechanism to an interfacial reaction controlled mechanism as the temperature increasing. The morphology and size can be controlled by setting the calcination temperature and the soaking time.