控制NH_4VO_3分解及产物间反应制备VO_2的研究

Research on Preparation of Vanadium Dioxide by Controlling Ammonium Metavanadate Decomposition and Reactions between the Products

VO2是一种温感相变材料,68℃左右它从低温半导体相向高温金属相转变,同时其光学和电学性质发生突变。由于V与O之间可以形成任意化学配比的VxOy,所以纯VO2的制备过程复杂难以控制。采用单一原料NH4VO3,在化学计量反应计算的基础上将其装入刚玉坩埚,置于特制的高压釜中,升温至1000K,反应60min,自然冷却得蓝黑色VO2样品。利用X射线衍射、扫描电镜和差示扫描量热法对样品进行表征与测试,结果表明,所制备的样品为VO2多晶粉末,粒度为几至几十微米,具有相变特性,相变温度为343.53K,相变过程是吸热过程,相变焓为43.75J/g。目前,该方法是合成VO2研究中最简单易行的方法。

VO2 is a phase transition material depending on temperature, at about 68℃ it goes through a transi tion from low-temperature semiconductor to high-temperature metal phase and accompanied by an abrupt change of its optical and electrical properties. Due to the fact of that V and O can form arbitrary stoiehiometric VxOy, it is difficult and complicated to prepare pure VO2. Single NH4VO3 is used to be the starting material. On the base of stoichiomet- ric reaction calculation, NH4 VO3 is loaded in a ceramic crucible and it is put in a special autoclave, then the autoclave is heated to 1000K and kept for 60min, finally it is naturally cooled down to dark blue VO2 sample. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC） are used to characterize and determine the VO2 sample. The results show that the synthesized VOe sample is polycrystal powder distributed from several micrometers to several decade micrometers, and it has the phase transition property. The phase transition temperature is 343.53K and phase transition enthalpy is 43.75J/g. Now it is the simplest and practical method for synthesizing VO2.