WO3-SiO2复合薄膜的烧结温度–相组成–气敏特性关系

RELATIONSHIPS AMONG SYNTHESIS TEMPERATURES AND PHASES COMPOSITION AS WELL AS GAS SENSING PROPERTIES OF WO_3-SiO_2 COMPOSITE FILMS

以钨酸和正硅酸乙酯(tetraethyl orthosilicate,TEOS)为原料,采用改进的溶胶–凝胶工艺,在Al2O3基底上制备WO3–SiO2复合薄膜,重点考查复合薄膜的烧结温度、物相组成及气敏性三者之间关系。用X射线粉末衍射仪和场发射扫描电子显微镜表征复合薄膜的微观结构,结果表明:在烧结温度为500℃与650℃时,复合薄膜为立方相和正交相混合相,复合薄膜的晶粒尺寸为25～30nm,分布均匀。650℃烧结时,对还原性挥发性有机化合物(volatileorganiccompounds,VOCs)气体中丙酮具有较好的敏感性。750℃烧结时,复合薄膜只有单一的正交相,晶粒尺寸在30nm左右,此时复合薄膜对氧化性气体NO2具有很好的敏感性与选择性,最低响应浓度(体积)为10–7,响应时间为2s,恢复时间约为10s。

Tungsten trioxide-silicon dioxide composite films,with H2WO4 and tetraethyl orthosilicate （TEOS） as the starting materials,were prepared on Al2O3 substrates through the improved solgel technology. The sintering temperature,phase composition and gas sensing properties of WO3–SiO2 composite films were studied systematically. The crystallite composition and micro-morphology of WO3–SiO2 composite films were analyzed by the X-ray diffraction and scanning electron microscope. Nanocrystalline WO3–SiO2 composite films synthesized at 500 ℃ and 650 ℃ have both cubic and orthorhombic phases,and the gain size is from 25 nm to 30 nm. WO3–SiO2 thin films synthesized at 650 ℃ presents better gas sensitivity for acetone in reducing VOCs gases. The WO3–SiO2 thin film synthesized at 750 ℃ has single orthorhombic phase and its crystalline size is about 30 nm. Meanwhile,the film exhibits good gas sensitivity and selectivity for NO2,and has shorter response and recovery times （2 s and 10 s,respectively） to low concentration （in volume） of NO2 gas （10–7）.