The Thermoelectric Properties Of Skutterudite-based Materials By High-temperature And High-pressure Method

The efficiency of a TE device can be defined by the dimensionlessthermoelectric figure of merit, ZT=S2·σ·T/κ，Where S stand for the Seebeck coefficient, σ is the electrical conductivity and κ represent the totalthermal conductivity. At the same time, σS2characters the electric properties.Skutterudite (CoSb3) materials have attracted wide attention since it wasproposed. The methods at ambient pressure have many limits to prepareSkutterudite (CoSb3) materials, because it is a process of Peritectic conversion.But the method of High-Pressure and High-Temperature has many advantagesin the preparation of materials. In this study, we prepared thermoelectricmaterials by HPHT method and quenching method. First of all, we synthesizedCoSb3skutterudite compounds by High-Pressure and High-Temperaturetechnique. The samples were characterized by X-ray diffraction, whichindicated that Polycrystalline Skutterudite with a bcc crystal structure wasprepared. The SEM indicated that the samples have abundant grain boundariesand the crystal grain sizes vary between1-2um.Secondly, we prepared the system Co4Sb11.7Te0.3at many pressure points atthe fundament of pure CoSb3skutterudite. The electrical resistivities, Seebeckcoefficients and power factor of the samples were measured in the roomtemperature. The thermoelectric properties of the samples were measured inthe temperature range of300-743K. The power factor is increasing withincreasing temperature. The highest power factor of19.04W·cm-1·K-2wasobtained at743K. The thermal conductivity of samples decreased withincreasing of temperature. The lower samples’ thermal conductivity4.13W·m-1·K-1was obtained at743K. Ultimately, we calculate the material ZTof0.34at a temperature of743K. The tellurium replacement can effectivelyreduce the materials resistivity and thermal conductivity, and ultimatelyenhance the value of the thermoelectric figure of merit of the material. We canconclude that chemical doping with Te at the Sb site the system Co4Sb11.7Te0.3can improve the thermoelectric performance by enhancing the electricityproperties and decreasing the thermal conductivity.The thermoelectric properties of Ba-filled CoSb3skutterudite thermoelectric materials was studied based on the tellurium of the replacementSkutterudite prepared by high temperature and high pressure method. Thesamples were characterized by X-ray diffraction, which indicated thatPolycrystalline Skutterudite with a bcc crystal structure was prepared. SEMtests showed that the grain boundaries of the material are abundant and grainparticle diameter vary about1-2um. We study the electrical propertiesdependence of concentration of Ba atoms. We studied the electrical propertiesof the material at room temperature with barium filling amount of variationand analysis of its physical reasons. The test of sample’ thermoelectricproperties carried out in the temperature range of300K-743K. The highestpower factor is for the barium filling amount of0.5and a temperature of743K,26.6μWcm-1·K-2. Simultaneously, the thermal conductivity is lowered as thetemperature rises. The lowest thermal conductivity of2W/(K·m) was obtainedin Ba0.4Co4Sb11.7Te0.3sample at743K, which is the lowest point in the bodymaterials. A maximum ZT value of0.87was obtained in Ba0.4Co4Sb11.7Te0.3sample at the temperature of743K.