钠钨青铜Na_xWO_3(x～0.88)纳米晶的机械化学法制备研究

Na_xWO_3 (x～0.88) nanocrystalline powders fabricated by mechanochemical synthesis

利用机械化学法合成了平均粒径为17nm的钠钨青铜NaxWO3(x～0.88)纳米晶材料。高纯Na片和WO3粉末经过行星式球磨机1h高能球磨,有固相反应Na+WO3→NaxWO3+Na2WO4发生。反应经过44h基本完成。利用去离子水洗涤后可得到纯净的钠钨青铜粉末。182W穆斯堡尔谱在77K温度下为一单线峰,显示样品为立方晶体结构。电性质测量表明样品的电阻率随着温度降低而升高,呈半导体特征,并可用三维可变程跃迁模型来描述。

Nanocrystalline powders of sodium tungsten bronze NaxWO3 (x-0.88) have been prepared by mechanochemical process. The solid-state reaction Na+WO3&rarrNaxWO3 + Na2WO4 proceeded with increasing milling time and was almost finished after 44 h. A single phase of NaxWO3 nanoparticles with average size of 17 nm was directly obtained by a simple washing process. The sample displays semiconducting behavior in the temperature range from 77-300 K, and the experimental data of resistivity can be described by Mott's three-dimensional (3D) variable-range hopping model. The 182W Mossbauer spectrum recorded at 77 K exhibits a singlet with an isomer shift of 0.0128 mm/s, indicating the cubic symmetry of NaxWO3 phase.