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Thermoelectric properties of nano - PbTe under high pressure

Author: ZhangXiangGuo
Tutor: DingZeJun；ZhangZengMing
School: University of Science and Technology of China
Course: Condensed Matter Physics
Keywords: PbTe Thermoelectric properties Thermoelectric materials Nano Under high pressure Thermal emf Hydraulic press First-principles calculations Pressure Calibration Power factor Electrical control system Preparation method The phase transition point Plugs High Pressure Physics Basic properties thermoelectric Band theory Thermocouple measurement Resistance Variation
CLC: O469
Type: Master's thesis
Year: 2009
Downloads: 61
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Abstract

In this thesis, the thermoelectric properties of PbTe nano-materials under high pressure. With the 400t four-poster double cylinder hydraulic press and since the formation of the measuring device to measure the electrical and thermal electromotive force of the nano-PbTe with increasing pressure. The results show that the conductivity increases with increasing pressure, and the thermal electromotive force is reduced with the increase of the pressure, the conductivity increase to compensate for the decrease of the thermal electromotive force calculated power factor increases with the increase of the pressure. At the same time try to take advantage of the thermoelectric energy band theory analysis to explain the reasons for this change. In addition, first-principles material's band calculation results are in good agreement. Finally, the paper summarizes the innovation and improved outlook for the test system. Introduction section reviews the history of the development of the high-pressure physics and commonly used high-pressure test method and the basic nature and classification of the thermoelectric materials. The first tells the story of the development process of the high-pressure physics. Secondly piston cylinder and diamond anvil cell under the basic physical properties measurement method. Again given the three basic performance of the thermoelectric materials and characterization of thermoelectric materials pros and cons of parameters - thermoelectric quality ZT. The second chapter introduces the 400T four-poster double cylinder hydraulic machine history, maintenance, commissioning and pressure calibration and under high pressure thermoelectric materials research progress. First a brief history of 400t four-poster double cylinder press, followed by a detailed description of the principle of the large presses hydraulic system, electrical control system, and then give a big press pressure, pressure relief process and pressure calibration recovery and debugging steps. Which focuses on a set of standard operating procedures of a high-pressure calibration prepared with Bi-wire method - capillary tube assay, key equipment - the assembly of the electrode plugs, electrical control system improvements, self-exploration and high-pressure thermoelectric materials research history. The third chapter describes the Preparation of nano-PbTe thermoelectric materials, thermoelectric properties of high pressure, first-principles Fermi surface calculation. About the first measurement of the thermoelectric performance problems encountered and the solution 400t four-poster-cylinder press. Details of the second PbTe nano material preparation method of a water bath. Again shows the result of a measurement under high pressure. The results of the surface, the conductivity increases with the increase in pressure increases exponentially, while the linear increase of the thermal electromotive force with the pressure decreases, the power factor of the material increases with the increase of the pressure. At 0.8 GPa, an increase of 3 times; the thermoelectric theory at the same time, it is expected that the phase change material, the increase of the power factor can reach as many as 30 times before. Finally, the use of first-principles calculations of the the materials minimalist Fermi level with pressure change and a comparison of the same thermoelectric theoretical results in good agreement. Chapter IV summarizes the innovation of this thesis and the next step made forward.

Thermoelectric properties of nano - PbTe under high pressure

Abstract

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