| Thermoelectric (TE) materials, as a new functional materials, which can convertheat directly into electricity and vice versa, have a wide range of commercialapplications in power generation and semiconductor refrigeration fields. Bismuthtelluride and its alloys are the best TE materials near room temperature. It had amature development in recent decades. In the present work, starting from high puritybismuth, antinomy, tellurium and selenium, vacuum melting, crushing, melt spinning(MS) combining with Resistance Pressing Sintering (RPS) which was assembled byour own design, were adopt to prepare Bi2Te3based bulks. The effect of preparationprocess and the nominal composition on microstructure and TE properties of p-typebismuth telluride-based TE materials were investigated. And the kilogram classP-type Bi2Te3based bulk samples were obtained and the uniformity of samples wereexplored. Starting from the commercial ingot cutting waste powder, through washing,reduction, doping, smelting and RPS sinering process, the Bi2Te3based bulks withhigh figure of merit were prepared. The main conclusions are as follows:(1) Comparing bluks prepared by smelting and then direlty RPS with thesample fabricated by MS+RPS, the latter had significantly lower thermalconductivity, thereby enhancing the ZT values. The relative densities of all thesamples are above96%, confirming the RPS process is indeed a good tool forcompacting high densification Bi2Te3based alloys. For the (BixSb1-x)2Te3(x=0.44,0.48,0.52) and Bi2Te3-xSex(x=0.12,0.21,0.3), the best nominal composition underthis condition are Bi0.44Sb1.56Te3and Bi2Te2.7Te0.3, respectively. The maximum ZTvalue of1.17and0.84was obtained for the Bi0.44Sb1.56Te3and Bi2Te2.7Se0.3alloysprepared by MS+RPS. Different from the conventional hot pressing and sparkplasma sintering, the RPS method introduced here was more suitable for practicalindustrial application due to its cost saving and high efficiency.(2) The kilogram class P-type Bi2Te3based bulk samples with dimension of100×60×26mm3were obtained by smelting and RPS process. The sample withdimension of50×30×13mm3were cuted in different directions to examine themicrostructures and TE properties. The results show that the TE properties ofsamples at different five sites showed good uniformity, the electrical resistivity is 1.1~1.2×10-5.m, the seebeck coefficient is200~220μ Ｖ/Κ, the thermalconductivity is1.1~1.3W/m K and the ZT value nearing the room temperature is0.8~1.0.(3) Bi2Te3based cutting waste powders from cutting wafers were firstlyselected as raw materials to prepare p-type Bi2Te3based TE materials. Throughwashing, reduction, doping, smelting and resistance pressing sintering (RPS) process,p-type (Bi,Sb)2Te3alloy bulks with different nominal stoichiometry weresuccessfully obtained. The results showed that the carbon and oxygen can beremoved to some extent through washing, reduction, melting process, and thebeneficial elements can be preserved. The carrier content and corresponding TEproperties could be effectively adjusted by appropriate doping treatment. At lastly,the bulk with a nominal stoichiometry of Bi0.44Sb1.56Te3was obtained and its’dimensionless figure of merit (ZT) was about1.16at90°C. The new recycletechnology introduced here can also be used for the other waste products such astops and tails of single crystal bars, cutting debris and broken irregular squareparticles and so on. In addition, the recycling technology introduced here was greenand more suitable for practical industrial application. It can improve materialutilization and lower raw material cost of manufacturer. |
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