Study Of Fabrication And Related Mechanism Of Thermoelectric Material And Micro-Generator Based On Electrochemical Technique

As a special micro-power source, thermoelectric micro-generator is of interest for its applications in Micro-Electro-Mechanical Systems(MEMS). Electrochemical deposition(ECD) method took the advantage at the fabrication of thermoelectric material in micrometer scale. In this paper, the detailed reduction processes of Bi³⁺ and HTeO²⁺ were studied for the first time. And thermoelectric nanowires were also prepared by electrochemical deposition. On the basic study of thermoelectric material, detailed exploration was made to the design and fabrication process of thermoelectric micro-generator.The reduction process of Bi³⁺ and HTeO²⁺ ions was studied by cyclic voltammetry, cathodic polarization and electrochemical impedance spectroscopy(EIS). XRD and EDS methods were also used to analyze the deposits prepared under different potentials and provide evidence for the reaction mechanism. In solution with different concentration ratio of , the reduction processes differed a lot. Cyclic voltammetry was used to choose the optimum composition of solution to deposit CHTeO / CBi₂Te₃ compound and the morphology and composition of films prepared at different potentials were analyzed. The effect of the deposition potential and micro-zone size on deposition of Bi2Te3 into the micro-zones was studied and seebeck coefficients of the prepared films were measured.Based on the study of thermoelectric material, the structure of micro-generator was designed and fabrication process was proposed. By the use of MEMS process and electrochemical technique, various patterns and structures were realized, and a kind of micro-generator was fabricated successfully by connecting 256 thermoelectric units in series. The performance of the mciro-generator was measured and results showed that the voltage output was in direct proportional to the temperature gradient. As for the fixed temperature gradient, the power output reached a maximum value when the resistance of micro-generator was same as that of load.In the solution containing oxalic acid, high-purity aluminium was anodized to prepare alumina film with nano-pores. By adding additive into the oxalic solution, alumina film could be produced with smaller pore size, higher pore density and more regular pores structure. Taking the alumina film as template, Bi2Te3 waselectrodeposited into the nano-pores. The effect of potential, thickness of alumina film and pore size on the deposition process was studied. The composition of nanowires was analyzed by TEM and thermoelectric properties of the nanowire arrays were measured.A new type of thermoelectric micro-generator, which was composed of thermoelectric nanowires material, was designed and the feasible fabrication process was studied. A unique aspect that distinguishes our device from the conventional one was that thermoelectric nanowire arrays were firstly used to fabricate thermoelectric micro-generator. The reasons for the problems existed were analyzed for the future study to modify the fabrication process.