Preparation And Thermoelectric Properties Of Donor-doped Lead Sulfide

Thermoelectric materials applied in thermal power generation and electrical refrigeration can realize the conversion among thermal and electric.With excellent performance in working process,thermoelectric materials have drawn more attention of researchers.Thermoelectric materials with high performance have become research focus in recent years,especially in the condition of energy crisis,climate warming,energy saving and environmental protection.PbTe-based materials were most widely studied for thermoelectric power generation.Te element is a so rare element that cannot provide constantly.Relatively,S is a cheaper and more abundance element.Not only that,the thermoelectric performance of PbS is comparable to PbTe for their same crystal structures and similar band structures.However,thermoelectric property of pure PbS is not very good,and some measures are adopted to optimize a better property.At present,main dopants are ions with similar radius as Pb²⁺,which shows potential value to improve its thermoelectric property.In addition,mainly synthetic methods of PbS bulk materials are melt alloying,spark plasma sintering and hot pressure sintering.Methods above not only need high purity elements,but also require high working temperature.Based on issues above,this paper makes the following work:?1?PbS-based powder materials are synthesized by hydrothermal method.Bulk materials with uniform grain size and higher than 90%density are synthesized by microwave sintering.?2?The band gap of PbS doped with Ga³⁺is decreased,which indicates an increase in conductivity.The radius difference between Ga³⁺?62 pm?and Pb²⁺?120 pm?causes a larger lattice distortion,which would effectively reduce the thermal conductivity.Thermal conductivity of 1%Ga-doped sample is 0.84 W·m^-1·k^-1 at 723 K.?3?Choosing Cr³⁺?61.5 pm?as dopant not only has a similar doping effect as Ga³⁺,but also increases Seebeck coefficient through increasing free entropy carried by carriers.Thermal conductivity of 1%Cr-doped sample is 0.86 W·m^-1·k^-11 at 723 K.?4?Better performance has been confirmed as Bi³⁺doped in n-PbS.So,this work chooses Bi and Cl co-doped to study Pb_0.985Bi_0.015S_1-yCl_y?y=0.005,0.01,0.015?thermoelectric performance.The results show that Bi³⁺?103 pm?and Cl^-?181 pm?are doped as donor dopants.Because ion radius is only small difference.The conductivity of Pb_0.985Bi_0.015S_0.99Cl_0.01 is 590.1S·cm^-1 at room temperature.