BiCuSeO-based Oxychalcogenide And Its Thermoelectric Properties

Oxide thermoelectric effects enable direct conversion between thermal and electrical energy.It has a very important application prospect in the field of thermoelectric power generation and refrigeration,eonstant temperature control and temperature measurement.A new promising thermoelectric material,composed of nontoxic,naturally abundant,light,and cheap elements,is expected to play a vital role in extensive applications for waste heat recovery in a thermally stable atmosphere.BiCuSeO has been thought as a promising thermoelectric materials for its low thermal conductivity since it was found in 2010.But its electrical conductivity is also low,so this paper tried to use strategies such as self-vacancy,single doping and dual doping to enhance its electrical conductivity,which could improve the figure of merit ZT value simultaneously.First of all,the two-step solid state synthesis method was used to prepare BiCuSeO powders.The first step was to mix raw materials to be uniform by hands.The second step was to use the self propagating combustion(SHS)method in air.Then,the bulk material was prepared by spark plasma sintering(SPS).The maximum ZT value of the pure BiCuSeO material reached 0.50 at 873 K.The BiCuSe1+xO ceramic block was prepared by solid phase method combined with SPS process.In the air powder prepared by combustion method and self propagating,due to the low melting point of volatile selenium,so this paper also discusses the influence of selenium content on the properties of ceramics.From the results,the conductivity was improved,from 2.4 Scm-1 at room temperature to 4.1 Scm-1,and increased from 32 Scm-1 to 42 Scm-1 at 873 K.Little volatilization we can speculate the effect of selenium on the performance of ceramic blockThe Bi1-xCuSeO ceramic was prepared by solid state method with SPS technique.The electron vacancy increased so that the carrier concentration increased.The electrical conductivity increased from 6.7 Scm-1 to 11.6 Scm-1 at room temperature,and the electrical conductivity increased from 37.6 Scm-1 to 62.7 Scm-1 at 873 K,the ZT value increased to 0.7Bi1-xNaxCuSeO ceramic was prepared by solid state method with SPS process.With the introduction of sodium ions,the grain growth is more regular and the particle size decreases.Because Na+ is much easier to substitute than Bi3+,its thermal conductivity decreased and electrical conductivity improved.Its thermal conductivity decreased from 0.71 Wm-1K-1 to 0.57 Wm-1K-1 at 873 K,and electrical conductivity increased from 1.6 Scm-1 to 199.3 Scm-1 at room temperature.Although the overall Seebeck coefficient crippled,the ZT value increased from 0.4 to 0.7.Bi0.9-xPbxNa0.1CuSeO ceramics were prepared by solid state method and SPS process.Combining the low thermal conductivity got by Na doping with the high electrical conductivity through Pb doping,the thermoelectric properties of the samples improved by dual doping of Na and Pb.The final analysis of the data is not difficult to see that,with the increase of Pb concentration in the conductivity increased and thermal conductivity have increased,because the conductivity is higher than the thermal conductivity of the sample increases,the value of ZT increased to 0.73.