| In recent years, due to the worsening environmental pollution and energy crisis, research of new high-performance thermoelectric material and thermoelectric conversion technology relating to thermoelectric material has received much attention. Thermoelectric material is the functional material which can convert thermal energy into electricity directly. But thermoelectric material has not been used widely recently, which is mainly owing to low conversion efficiency of thermoelectric material. So, it is a new topic to develop a thermoelectric material of high conversion efficiency and expand its application. Zn4Sb3 is widely recognized as one of the most promising thermoelectric material. This study is to improve the thermoelectric properties of material by nanometer treatment and doping the rare earth elements which can improve the Seebeck coefficient.The electrochemical behavior of Zn (II), Sb (III) in electrolytic solution system which mainly contains ZnCl2, SbCl3, Citric acid as chelating agent was determined by cyclic voltammetry in this paper, Zn (II) and Sb(III) were found to be codeposited near the reduction potential -0.7V. On the basis of above, nano-film of Zn-Sb naniparticle-film thermoelectric material was producted by pulse electrochemical method by CHI602B analyzer providing pulse voltage. Influence of pH value, temperature, concentration of salts, duty cycle, current density and doping rare earth element on the content of Zn, Sb in electrodeposition film and the apparent morphology of material were investigated. Results showed that pH was in 1.0～3.0, 25℃～40℃for temperature, 5%~10% for duty of cycle pulse electrodeposition, the predominant salt /()2 +2+3+n Zn nZn+ nSb in molar varied between 0.3 and 0.6, and current density of 1~7A/dm2 is appropriate, in the case of which alloy film whose surface is covered by a layer of smooth, dense, uniform particles obtained.The morphology of Zn-Sb alloy film prepared under the appropriate condition above were analysed by SEM, results indicated that film with an average particle size of about 100nm even refining were obtained, gap between particles of surface of film was tiny and distributed evenly, doping of La, Ce had an significant influence on fineness and uniformity of crystalline grain. X-ray diffraction analysis showed that the Zn-Sb alloy film producted by pulse electrochemical method is mainly consist of ZnSb, Zn4Sb3, DSC analysis showed that endothermic peak appeared obviouslys at 420℃, 495℃and 640℃, which are respectively maybe the Zn melting process, the Zn4Sb3 phase transition and the melting process of Sb, verifying XRD result. Lastly, building Zn4Sb3 crystal model, which was applied to the first principle-based plane wave pseudopotential density functional theory, band structure and density of states of Zn4Sb3 and La, Ce-dopied were obtained. Seebeck coefficient of material with variable temperature was calculated according to the improved Wangsag principle was compared to values experimental measured. The results showed that trend of Seebeck coefficient changes with temperature was consistent with which experimental measured. Doping La, Ce improved the Seebeck coefficient of the material. |
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