Effects Of Different Morphologies Of PbTe Nano-Powders On Bulk Thermoelectric Properties

Thermoelectric materials is a kind of function materials,which can be used as thermoelectric refrigeration and thermoelectric power generation.When the materials are in different temperatures, it can exchange the electricity and heat.The device made by this materials is non-pollution,longer life,good stability.Lead telluride is a traditional thermoelectric materials,which is be used in medium temperature area,and has higher thermoelectric properties.In this article,the hydrothermal method is used to product kinds of PbTe morphologies, such as nano-particles,funnel-shaped, rodlike,leaf-flower and so on,which can be got by controlling the technological parameter,such as reaction temperature,the kind and amount ofsurfactants,the sodium hydroxide concentration.Then the formation mechanism and forming process were analyzed and discussed.Finally, the nano-powders with different morphologies were hot-pressed into bulk samples,and their thermoelectric properties were measured.The specific research contents are as follows:(1)The experimental raw materials were lead nitrate,sodium tellurite,sodium borohydride.When changing process conditions,the results show that the higher reaction temperature, the surface indentation of funnel-shaped is deeper,even the edge fractures.When changing the kind of surfactants,it can be found that PVP has stronger surface modification effection,which has more complete funnel-shaped.With the amount of PVP increasing,the morphologies change from nano-particles to funnel-shaped.With the sodium hydroxide concentration increasing,the funnel-shaped is more uniform.We make the speculation from the forming process.It maybe that the surfactants are acted as the soft template,and the sodium hydroxide has the etching effection.From the dynamic angle,we think that the atoms of edges and corners grow quickly.(2)The experimental raw materials were lead nitrate,sodium tellurite,hydrazine hydrate.With the temperature increasing,the results show the mainly morphologieschange from the eight angle petal to the dendritic.When changing the kind of surfactants,the morphologie of PVP is the eight angle petal,but the morphologies of EDTA and SDBS are going to be the eight angle petal,which show that PVP has the stronger surface modification effect in same amount.When the sodium hydroxide concentration is one moles per litre and two moles per litre,the morphologies show the eight angle petal and leaf-flower respectively.When changing the sodium hydroxide concentration,the morphologies transform from the rodlike to the eight angle petal,then the leaf-flower.The all studies indicate that the leaf-flower is produced,because of the both of the sodium hydroxide of etching effection,the surfactants acted as the soft template and the dynamic angle.At last,the comparison between the hydrazine hydrate and the sodium borohydride showes that the hydrazine hydrateis is necessary for the eight angle petal.(3) The nano-powders with morphologies of funnel-shaped, rodlike and leaf-flower were hot-pressed into bulk samples,and the thermoelectric properties were measured.The results show that the bulk samples have different morphologies with the different powders. In the thermal conductivity,the leaf-flower is the lowest,the funnel-shaped is the highest.In the electrical property,the electrical resistivity and the Seebeck coefficient of funnel-shaped is highest.However,the leaf-flower is opposite.With the formula computing,the pyroelectric merit of the leaf-flower is 0.97,which is the highest.It is higher than the recognize of 07~0.8.