Nano Pbte Under High Pressure Thermoelectric Properties

This work is mainly about the thermoelectric prosperities of nano-particle PbTeunder high pressure. The electrical conductivity and the Seebeck coefficients underhigh pressure were measured by using a piston cylinder type vessel could be operatedin two directions via 400t hydraulic press with double pistons and four pillars (PVHP)and a self- equipment. The results show: the electrical conductivity increase whilethe Seebeck coefficients decrease with the loading pressure. The increase of electricalconductivity makes up for the decrease of Seebeck coefficients. The calculated PowerFactor increases with loading pressure. The energy-band of thermoelectric theory istried to explain the phenomena. At the same time, the energy-band of PbTe was cal-culated based on the first principle. The measured and calculated results suggest theyhave good consistence. At last, we summarize the innovations and give the prospectIn the introduction, the development history of high-pressure physics, commonmeasuring method at high pressure as well as the basic properties and the categoriesof thermoelectric are introduced. Firstly, the history of high pressure introduced. Sec-ondly, the measurement under Piston-Cylinder and Diamond Anvil Cell (DAC) areintroduced respectively. At last, the three elementary properties of thermoelectric ma-terials and the Pros and cons parameters: thermoelectric merit ZT are given.The second chapter introduces the history of 400t high-pressure machine, main-tenance, debugging, pressure calibration and the progress of thermoelectric propertiesunder high pressure. The history of the 400t high-pressure machine is introduced atfirst; secondly, the principles of hydraulic pressure system and controlling circuit ofhigh-pressure machine are described. Then the detailed stepping up, stepping downand pressure calibration processes are given. Especially, the new method to prepare Bithread, the setup of electrode chock plug, the innovation of the controlling circuit, astandard operations and the progress of thermoelectric properties under high pressureThe third chapter mainly describes the preparation of nano-particle PbTe, the ther-moelectric proprieties under high pressure, the calculation based on the first principle.First are the problems and the solutions of thermoelectric properties under PVHP. Sec-ond is the preparation of nano-particle PbTe by using low temperature aqueous chem-ical route. Third are the results of sample under high pressure. The results suggest the electrical conductivity increase exponentially while Seebeck coefficients decreaselinearly with pressure. The Power factor increase with loading pressure and it is threetimes under 0.8GPa than at ambient pressure. It is predicted that the power factor reachto 30 times than at ambient pressure before phase transition according to thermoelec-tric theories. At last, the contracted Femi energy calculated based on first principle hasa good Consistency with the result by using thermoelectric theories.At the last, the main work and creative points of this thesis is concluded, and thefuture work in prospect is given.