Synthesis And Thermoelectric Properties Of Beta-Zn₄Sb₃ Nanowires And Nanorods

As a promising middle temperature thermoelectric material,beta-Zn₄Sb₃ has become to a research focus.In this thesis,we have synthesized Beta-Zn₄Sb₃ granule and nanaowires/rods.The as-synthesized samples were investigate by scanning electron microscopy(SEM),transmission electron microcopy(TEM),X-ray diffraction(XRD) and thermoelectricity capability testing apparatus.The main conclusions are listed as follows:1) We have synthesized Beta-Zn₄Sb₃ in vacuum by solid reaction and rubbing samples in different time.We find that:when the diameter of granule decreases,distinct reducing of thermal conductivity of the sample appears.In 700 K,thermal conductivity of the nanoparticles with diameter of 500nm is 0.76W·m^-1·K^-1.Using account expressions,we can find the figure of merit(ZT) of the sample is 1.0.2) Using the synthesized beta-Zn₄Sb₃ nanoparticles as former body,we have synthesized beta-Zn₄Sb₃ nanowires/rods.The diameter of nanorods is 300 nm and length up to several micrometers while the diameter of nanowires is 100 nm and the length is several decades um.Electrical resistivity and Seebeck coefficient as the function of temperature were investigated and the numbers were not different from the synthesized beta-Zn₄Sb₃ granule.But thermal conductivity has great reducing,in 700K thermal conductivity is 0.55W·m^-1·K^-1.It is found that thermal conductivity of the nanowires is much lower than that of the conventional powders,which can be explained by phonon-scattering elements at several length scales.As a result,the figure of merit(ZT) of nanowires is 1.4.When the synthesized beta-Zn₄Sb₃ nanowires were annealed in 750 K,thermal conductivity is 0.53 W·m^-1·K^-1 and the figure of merit(ZT) of the sample is 1.5.