Study On Thermoelectric Properties Of Tin-Based Materials

A thermoelectric material is a functional material that can directly perform thermoelectric energy conversion.Because of its many advantages,it has been successfully applied to a variety of energy-related fields,such as recycling of waste heat energy,Peltier refrigerators.The core of improving the performance of thermoelectric materials is to increase the ZT value of the material.However,it is determined that the ZT's various transport physical quantities have a mutually restrictive relationship,so the improvement of ZT is not an easy task.In order to avoid blind experimental attempts,basic research on its internal mechanisms is particularly important.One of the ways is the computational simulation of first-principles.This paper mainly uses the first-principles calculation method to calculate and analyze the electronic structure and thermoelectric transport properties of SnO materials.The main contents are presented as follows:1.Based on the first principle of density functional theory combined with Boltzmann transport theory,the electronic structure,thermoelectric and phonon transport properties of two-dimensional material SnO are discussed.It is found that the bulk SnO is an indirect band gap structure with a band gap of 0.484 e V.The electric effective masses are low due to the dispersive conduction band,and have a high mobilities.There have relationships between the power factor and degenerate electronic conduction structure.We also found that the bulk SnO is anisotropic,the value of the lattice thermal conductivity at room temperature?300K?is K_L^x=K_L^y=10.79W/mK,K_L^z=3.53W/mK.The lone pairs of Sn are responsible for anharmonic interactions,so the Tin-based materials have a low lattice thermal conductivity.2.Using the first principle,we also calculated the electronic structure and thermoelectric properties of a single-layer SnO material.Single-layer SnO was also found to be an indirect band gap with a band gap of 3.0 e V.Due to the large band gap and flat structure,the effective masses of single-layer are larger than the bulk.The lattice thermal conductivity of the single-layer SnO was 0.8 W/mK at 300K.At the same time,the electron mobility of phase b of single-layer SnO is about 10²cm²v^-1s^-1.So the single-layer SnO is a potential thermoelectric material.Finally,the fourth chapter gives the summaries and prospects of this thesis.