碲化铋热电薄膜的制备及物性研究

发布时间：2018-07-13 12:13

【摘要】：热电材料是可以将热能转化成电能的材料,在温差发热和制冷上被广泛应用。理论研究和实验探究均表明降低材料维度可以有效提高材料热电转化效率。碲化铋基化合物是目前室温下性能最好的热电材料。本文采用高真空热蒸发镀膜法,以高纯碲化铋粉末为蒸发源,在衬底380℃蒸发源360℃镀膜反应5min即可制备出尺寸较大且均匀的碲化铋拓扑绝缘体纳米薄膜。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、高分辨率透射电子显微镜(HRTEM)等手段对镀膜生长10min的样品产物的形貌和结构进行表征,样品表面呈现出螺旋形貌的台阶生长三角结构纳米薄膜,台阶边缘生长出直立排列的片状结构,对其螺旋形貌生长机制进行了分析。使用原子力显微镜(AFM)对螺旋结构和直立排列的片状结构高度厚度进行统计测试。结果表明,镀膜生长10min的样品螺旋生长的台阶结构厚度大致为15-20nm,直立排列的片状结构厚度在40-80nm左右、高度大概在150-200nm左右。采用一步水热法,以Bi(NO_3)_3·5H_2O为Bi源,Na_2TeO_3为Te源,葡聚糖(分子量40000)为还原剂和碳包裹层,制备了不同Bi和Te摩尔比的碲化铋样品。利用SEM、XRD、HRTEM对不同摩尔比样品的物相和形貌进行了表征。结果表明,Bi的摩尔百分比会影响产物最终的形貌。随着Bi的摩尔百分比的升高,样品形貌趋向于生长为二维结构。对Bi:Te=1:3碳加入量不同的样品进行光催化测试,碳含量为0.03mmol时降解率达到87.5%。对碳含量为0.02mmol而Bi和Te摩尔比不同的样品进行光催化测试,Bi:Te=1:2降解率最高,达到70.8%。对纳米线的生长机制进行了阐述。
[Abstract]:Thermoelectric materials, which can convert heat energy into electric energy, are widely used in temperature difference heating and refrigeration. Both theoretical and experimental studies show that reducing the material dimension can effectively improve the efficiency of thermoelectric conversion. Bismuth telluride compounds are the best thermoelectric materials at room temperature. In this paper, large and uniform bismuth telluride topological insulator nanocrystalline films were prepared by high vacuum thermal evaporation method and high purity bismuth telluride powder as evaporation source. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) were used to characterize the morphology and structure of 10min films. The growth mechanism of the spiral morphology of the flat structure with vertical arrangement on the edge of the step was analyzed. Atomic force microscopy (AFM) was used to measure the height and thickness of helical and vertical lamellar structures. The results show that the thickness of spiral growth of 10min is about 15-20 nm, the thickness of vertically arranged sheet structure is about 40-80nm and the height is about 150-200nm. Bismuth telluride samples with different Bi and Te molar ratios were prepared by one-step hydrothermal method with Bi (no _ 3) _ 3H _ 2O as Bi source and Na _ 2TeO _ 3 as Te source, dextran (molecular weight 40000) as reducer and carbon encapsulation layer. The phase and morphology of the samples with different molar ratios were characterized by means of SEM-XRD- HRTEM. The results show that the mole percentage of Bi will affect the final morphology of the product. With the increase of the molar percentage of Bi, the morphology of the sample tends to grow into two dimensional structure. The photocatalytic test was carried out on the samples with different carbon content of 1: 3: 1: 3, and the degradation rate reached 87.5% when the carbon content was 0.03mmol. The photocatalytic test was carried out on the samples with carbon content of 0.02mmol and different molar ratio of Bi and Te. The degradation rate of Bi: Te1: 2 was the highest, reaching 70.8%. The growth mechanism of nanowires was described.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O484

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