能源短缺以及環境污染問題越來越嚴重，尋找替代性能源方案是刻不容緩。熱電發電原理根據某些材料特有的熱電(Thermoelectric)特性，材料在無做功的情形下，可以將熱能和電能做互相轉換。半導體熱電材料發電模組係根據 Seebeck 熱電原理，只要在材料兩端建立溫度差，發電模組的線路即可獲得電位差，此現象不須外加做功即可將熱能轉換電能，具有體積小、無做動部件、無噪音、無汙染、維修成本低廉等優點。熱電材料的優劣取決於材料的 ZT 值，Z是熱電優值(Figure of merit)，定義為 α2σ/κ，其中α=ΔV/ΔT，為材料的Seebeck 係數；σ 是材料的導電率；κ 是材料的導熱率，T 是絕對溫度。因此可以看出一個優良的熱電材料需要高Seebeck 係數、高導電率、低熱傳導率。現階段而言，熱電值大多在 1以下，無法有更出色的應用，本研究將利用急冷旋鑄法製備具有奈米晶粒 Zn4Sb3 中溫型熱電材料粉末，並以熱壓燒結製作具有奈米結構的熱電塊材，以求增進功率因數(α2σ)和降低熱導性，最後探討熱電材料在不同急冷旋鑄條件下之晶粒尺度、微結構的不同以及利用不同熱壓粉末燒結條件對熱電塊材特性之影響。The problems of energy shortage and environment pollution are going seriously. It is important to find alternative energy source project. Thermoelectric materials have thermoelectric properties that can transport heat energy to electric energy without external work. Semiconductor thermoelectric materials power generator is working under Seebeck thermoelectric Law. By establishment of the temperature difference across the materials circuit, we can get voltage across power generator. The advantage of this technology is small volume, quiet, no vibration, no pollution and low maintenance cost. Thermoelectric materials properties can be defined as the figure of merit. The figure of merit is defined as ZT = α2σ/κ, where α is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity and T is the temperature in Kelvin. Therefore, a good material should possess high electrical conductivity, large Seebeck coefficient and low thermal conductivity to retain the heat at the junction and to reduce the heat transfer losses. Most of thermoelectric materials’ ZT value are lower than 1. They do not have potential for commercial application.The purpose of this program will prepare high performance medium-temperature thermoelectric alloy powder, Zn4Sb3 with nano-structure by means of rapidly-quenched melt-spinning (MS) technique. Then, these rapidly quenched nano-structured alloy ribbons will be ball milled into fine powder and pressed by hot pressing under vacuum to form the bulk samples. The final product fabricated via this new process is expected to increase its power factor ( α2σ ) and reduce thermal conductivity in comparison with the conventional process. In addition, the relationship between the microstructure (grain size) of alloy and its process condition as well as the effect of microstructure on the thermoelectric performance will be investigated.
