Preparation And Characterization Of Bismuth Telluride Thermoelectric Films

Thermoelectric materials could convert thermal energy into electrical energy,which widely used in thermoelectric power generation and cooling.Theoretical and experimental studies have shown that reducing the dimension of the material can effectively improve the thermoelectric conversion efficiency of the material.The bismuth telluride compound is the best thermoelectric material at room temperature currently.In this paper,the nano films with large size and uniformity were prepared by high Vacuum thermal evaporation that substrate at 380 ?,evaporation temperature of 360 ? for 5 min.The morphology and structure of the samples were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?and high-resolution transmission electron microscopy?HRTEM?.The surface morphology of the samples was characterized by a spiral morphology,and Step edge grow with vertical lamellar nanostructure.The growth mechanism was analyzed.The atomic force microscopy?AFM?was used for statistical testing the thickness of the helical structure and the height of the vertical lamellar structure.The results show that the thickness of the step structure is about 15-20 nm,and the thickness of the lamellar structure is about 40-80 nm,and the height is about 150-200 nm.Bismuth telluride samples with different Bi and Te molar ratios were prepared by one step hydrothermal method which using Bi?NO₃?₃ ? 5H2 O as Bi source,Na₂TeO₃ as Te source.Dextran?MW40000?as reducing agent and carbon coating.The phase and morphology of different molar ratios were characterized by SEM,XRD and HRTEM.The results show that the mole percent of Bi affects the final morphology of the products.With the increase in the mole percent of Bi,the morphology of the sample tends to grow into a two-dimensional structure.When the molar ratios of Bi: Te = 1: 3,the photocatalytic activity of samples what carbon mass was different,and the degradation rate was 87.5% when the carbon content was 0.03 mmol.The degradation rate of Bi: Te = 1: 2 was 70.8%,while the samples with carbon content of 0.02 mmol but different molar ratio of Bi and Te were photocatalytic.The growth mechanism of nanowires was described.