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Syntheses and Properties of Nanostructured Bi2Te3 Based Thermoelectric Materials

Author: JiXiaoHua
Tutor: ZhaoXinBing
School: Zhejiang University
Course: Materials Physics and Chemistry
Keywords: Thermoelectric materials Bi2Te3 Nanotubes Nanocapsules Nanostructured Nucleation and growth mechanisms Homogeneous nanocomposite Solvothermal synthesis Hydrothermal Synthesis Low temperature wet chemical synthesis Hot Thermoelectric properties Figure of merit Rare earths
CLC: TB383
Type: PhD thesis
Year: 2005
Downloads: 1257
Quote: 14
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Abstract


Thermoelectric materials is a way to achieve direct conversion between heat and power semiconductor functional materials, thermoelectric cooling thermoelectric power generation and has important application areas such as value and broad application prospects. Bi2Te3-based compounds of the highest dimensionless ZT value close to 1, is the application of the best around room temperature thermoelectric materials. Nano thermoelectric materials because of their lower thermal conductivity lower than the conductivity of more significant, the thermoelectric figure of merit can be increased significantly. In this paper, solvent heat, hot water and other low-temperature wet chemical synthesis method to prepare novel Bi2Te3 based nano powders synthesized with different forms of Bi2Te3 hollow shell-like nanostructures including Bi2Te3 nanotubes and nanocapsules, etc., and were prepared containing rare earth elements The Bi2Te3 base (RE-Bi2Te3) alloy nano-powders. Application of XRD, SEM and TEM on the synthesis of nano-powders structural and morphological analysis, experimental studies and Bi2Te3 are discussed in detail in the process of hydrothermal synthesis reaction mechanism of nucleation and growth mechanism. Prepared by vacuum hot pressing bulk thermoelectric materials and bulk nanocomposite thermoelectric materials, and measured the thermoelectric properties of hot samples. The most important result of this work is the synthesis of Bi2Te3 nanotubes and nanocapsules, which was first seen reported Bi2Te3 hollow shell-like nanostructures. Hydrothermal synthesis at 150 ℃ Bi2Te3 nanotube diameters of 25-100 nm, lengths up to several microns. Observed that the nanotube wall is a spiral upturned, wall Bi2Te3 lattice (003) crystal surface was a pipe axis about an angle of 20 °. By the low-temperature wet chemical method to synthesize hollow nanosphere irregular size of about 10-50 nm. This work is the second important result is presented and prepared with a high figure of merit advanced Bi2Te3 based nanocomposite thermoelectric materials. This paper proposes a \The results show that homogeneous nanocomposite thermoelectric materials can maintain the electrical properties of the case significantly lower thermal conductivity. Experimentally measured homogeneous nanocomposite sample the lowest thermal conductivity of only 0. 8 W ??· m-1 · K-1, the highest dimensionless ZT value at 420K temperature reaches 1.25. It is reported bulk Bi2Te3 based thermoelectric materials of the highest ZT values. Rare earth chlorides or oxides of rare earth precursors, solvothermal synthesis containing rare earth RE-Bi2Te3 nanopowders. Powder particle size of 30 nm are mainly the following irregular polyhedron. Solvothermal synthesis / sintered resulting single-phase RE-Bi2Te3-based alloys and binary Bi2Te3 have the same lattice type and similar lattice parameters, indicating that the solid solution of rare earth elements has Bi2Te3 crystals. The prepared paper samples RE-Bi2Te3 are n-type, indicating that the rare earth element doped semiconductor for the donor. Thermal conductivity measurement shows alloyed rare earth Bi2Te3 Bi2Te3-based compound to reduce the thermal conductivity. This series of experiments the maximum ZT value at 450K sample Ce-Bi2Te3 obtained when ZT ≈ 0. 22. Respectively, ethylenediamine (en), N, N-dimethylformamide (DMF), pyridine, acetone, ethanol and deionized water as the reaction medium, solvents Synthesis of Bi2Te3 nanopowders. Discusses the physical and chemical properties of solvent for the synthesis of nano Zhejiang University PhD thesis nanostructures BiZTe3 based thermoelectric materials synthesis and properties of powder formation and morphology. Experimental results show that the deionized water has a high dielectric constant, surface tension and the size of a small molecule synthesis of single-phase BiZTe: the best solvents. Studied a plus \product nanorods or nanoribbons size has grown up as the temperature rises no obvious, which is considered to be on the block with Te precursor cleavage crack related debris. pair BiZTe3 hydrothermal synthesis reaction mechanism was studied. NaOH alkaline additive in the reaction plays a more important role, Te powder containing a reducing agent in a strongly alkaline solution will dissolve and form a colloidal compound pounds in the reaction with a BiZTe3 that both Bi Te atoms and the bond between atoms have Bi3 and TeZ a reaction between ions through carefully designed experiments studied the hydrothermal synthesis BiZTe3 nanocrystals nucleation and growth mechanisms for different synthesis conditions, proposed \lateral growth, and there is the \Different forms of BiZTe3 nanoparticles formed discussed. Keywords: thermoelectric materials; BiZTe3; nanotubes; nanocapsules; nanostructures; nucleation and growth mechanisms; homogeneous nanocomposite; solvothermal synthesis; hydrothermal synthesis; low temperature wet chemical synthesis; pressing; thermoelectric properties; figure of merit; 'RE

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