柠檬酸溶胶法制备Bi_2WO_6粉体及其表征

Preparation and characteristics of Bi_2WO_6 powders by citrate sol process

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Bi_2WO_6粉体.热重-差热(TG-DTA)和红外光谱(FT-IR)分析Bi_2WO_6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Bi_2WO_6粉体结构、形貌进行表征.结果表明,Bi_2WO_6前驱体热分解分为4个阶段,其中Bi_2WO_6粉体开始形成发生在367℃.Bi_2WO_6前驱体在400~700℃煅烧5 h获得了单一的Bi_2WO_6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.

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.