Synthesis And Thermoelectric Properties Of Ag And In Codoped PbTe-based Compound

Recently, a significant progress has been achieved in the research on PbTe-based compound, AgPb_mSbTe_m+2 compounds propared by Ag and Sb Codoping to PbTe show a much higher thermoelectric performance than binary PbTe alloy. However, the influence of other atoms codoping on the structure and properties of PbTe-based compounds has rarely been investigated. In this thesis, n-type Ag and In codoped PbTe-based and p-type AgIn codoped Pb_1-xSn_xTe-based compounds were synthesized by melting and slow cooling method, the influence of Ag and In codoping on the structure and thermoelectric properties of compounds were investigated. The following results have been obtained in this thesis:(1) n-type Ag and In codoped PbTe-based compounds: for In_xPb_1-xTe compounds, electrical and thermal conductivity increase, Seebeck coefficient decreases with the increasing of x; for (AgIn)_xPb_1-2xTe compounds, electrical and thermal conductivity decrease, Seebeck coefficient increases as the Agln concentration increases; for the non-stoichimetric Ag_1-xPb_18+yInTe₂₀ compounds, electrical conductivity increase with the decreasing of Ag content and increasing of Pb content. For all the Ag and In codoped PbTe-based compounds, (AgIn)_0.01Pb_0.98-Te show the best performance, with a maximum ZT value of 1.1 at 800K.(2) p-type Ag and In codoped Pb_1-xSn_xTe-based compounds: for (AgIn)_x(Pb_0.5-Sn_0.5)_1-2xTe compounds, the Agln concentration has a significant impact on the lattice thermal conductivity that decreases as Agin concentration increases; for Ag_0.5Pb5Sn₄In_xTe₁₀ compounds, carrier concentration could be tuned in a wide range, when x decrease from 0.5 to 0.3, carrier concentration increases from 4.86×10¹⁸cm^-3 to 3.85×10²¹cm^-3 at 300K, cartier scattering mechanism changes from an acoustical phonon scattering to an ionized impurity, thermal conductivity is gradually dominated by carrier; for Ag_0.5(Pb_8-xSn_x)In_0.5Te₁₀ compounds, carrier concentration increases and mobility remains constant about 80cm²/Vs as the increasing of Sn at 300K, when the pb/Sn ratio equals to 1:1, the lattice thermal conductivity show a minimum and could decreases further aider spark plasma sintering. For all the Ag and In codoped Pb_1-xSn_xTe-based compounds, Ag_0.5Pb₅Sn₄In_0.3Te₁₀ show the best performance, with a maximum ZT value of 1.2 at 800K.