Preparation Of InSb And CuInSe₂ Based Semiconductor Materials And Their Thermoelectric Properties

Thermoelectric?TE?materials has wide application prospects on account of its promising application to directly convert waste heat into electricity,thus solving the human energy shortage.In recent years,due to the staged progress of In-doped and In-based compounds as thermoelectric materials,we selected InSb and Cu InSe₂thermoelectric materials to investigate their thermoelectric properties,and improved their thermoelectric properties by changing preparation conditions and doping methods.And then improve the conversion efficiency of thermoelectric devices,to achieve commercial application as soon as possible.In this work,we offered a new strategy of eutectic melting to improve the TE properties by melting method.By introducing Sb vacancies,the thermal conductivity was reduced and TE properties was improved.The InSb–In eutectic structure has been introduced by addition of excess In into the InSb matrix to modulate the TE performance of InSb.With the increase of In content,both the electrical conductivity and Seebeck coefficient show a tiny increase due to the change of carrier concentration,and the highest ZT value of InSb_0.95 reaches 0.4.The CuInSe₂ powder was synthesized by solvothermal method,and the crystal grains were fine in the order of submicron to micrometer,and the grain size was 300-500nm.The CuInSe₂/In₂Se₃ bulk samples were prepared by spark plasma sintering technique?SPS?,and the sintered samples are compact and the fracture morphology is regular.By adjusting the hydrothermal process parameters,the effects of hydrothermal process parameters such as synthesis temperature and reaction time on the morphology and grain size of Cu InSe₂ powder were systematically studied.The Seebeck coefficient increased significantly in composite thermoelectric materials,up to 200?V·K^-1 at 623K.The thermal conductivity of the sample significantly decreases from the room temperature to 700 K.The results show that the bulk thermal and electrical properties of the CuInSe₂ nanopowder obtained by hydrothermal method are not very high after sintering.The Cu InSe₂ bulk composite by solvothermal method achieves the highest ZT value of 0.187 at 700 K.So we optimized the preparation method and used doping to change the thermoelectric properties.On the basis of low thermoelectric properties of synthetic samples in hydrothermal method.,we changed the preparation process method,the polycrystalline Cu InSe₂based bulk materials were synthesized by conventional solid-state reaction and spark plasma sintering.This work optimized compositions and improved thermoelectric properties of CuInSe₂ by manufacturing cation vacancies(V_Cuu and V_In).The Cu_0.99InSe_2.05 bulk sample achieves the highest ZT value of 0.31 at 773 K,which is 3times higher than that of pristine CuInSe_2.05 by the introduction of Cu vacancies increases the Seebeck coefficient.Moreover,it is the highest ZT value in Cu InSe₂system in all of previous literatures.