Liquid Phase Synthesis Of PbTe And Ag_nPb_mM_nTe_m+2n（M=SB, Bi, La） Thermoelectric Material And Their Mechanisms

Thermoelectric material is a kind of functional material that transformingthermal energy to electricity directly, which has crucial application value in thefield of thermal energy conversion and thermoelectric refrigeration. PbTe and itsalloys，which have the highest dimensionless figure of merit about2.2as reported，are known as one of the best TE material currently available at mediumtemperature. So far, the methods for the preparation of AgnPbmMnTem+2n(M=Sb, Bi,La) materials are mainly melt cooling method and mechanical alloying method,these two routes are hard to operate at high synthetic temperature and difficult tocontrol the morphologies and sizes of the as-prepared samples. Since the sizes andmorphologies have key influence on the thermoelectric properties of the materialsand the figure of merit of TE materials could be significantly improved if thematerials were nanostructured and dimensionally reduced. Therefore, it is a newroute to improve the thermoelectric performance through controllable synthesislead tellurides nanomateriasl with specific size and morphology.In the present work, different PbTe and AgnPbmMnTem+2n(M=Sb, Bi, La)nanostructures with various morphologies, including hopper-like microcube,nanorods, nanosheets and other hierarchical superstructures have been synthesizedvia a hydrothermal method．Some factors, such as reaction time and temperature,the concentration of NaOH, surfactants, reductant. etc were investigated. Theformation mechanisms of different PbTe and AgnPbmMnTem+2n(M=Sb, Bi, La)nanocrystals were proposed based on the time-dependent experiments．The transport properties of the PbTe and AgnPbmMnTem+2n(M=Sb, Bi, La)nanocrystals reveal the as-prepared samples display typical semiconductorcharacter, showing the electrical conductivity increases with the rising temperature,according to the thermal excitation mode.The present research works are not only useful for the synthesis and theoptimization of PbTe and AgnPbmMnTem+2n(M=Sb, Bi, La) nanocrystals via ahydrothermal method, but also have guiding significance for the otherthermoelectric materials.