β-Zn4Sb3為熱電性能表現最佳的中溫熱電材料，為提升其熱電優值，本研究中混和具有奈米晶與微米晶結構的Zn4Sb3粉末，藉由增加塊材內部晶界面來降低塊材導熱度，進而提高熱電轉換效率。首先將急冷旋鑄法製備具有奈米晶的Zn4Sb3薄帶研磨成粉末後，再與熔融法製備的微米晶粉末互相混合，其Zn4Sb3粉末混合比例以奈米晶/微米晶：95/5 vol.%、90/10 vol.%、85/15 vol.%與80/20 vol.%為基準預製混和粉末，再利用真空熱壓法燒結成相對密度約為99.5%以上之Zn4Sb3塊材，使其具有高的破裂韌性可達1.46 MPa．m1/2。藉由奈米晶的晶粒細化來增加Zn4Sb3材料Seebeck係數與降低熱傳導率，同時利用添加微米晶的來增加載子的移動進而提升電導率，由於奈米/微米複合結構不但降低了材料的晶格熱導率並同時提升了電導率，進而提高整體之ZT值。研究結果顯示80 vol.%奈米晶/20 vol.%微米晶複合結構熱壓塊材在325℃表現出最高ZT值為1.22。;The β-Zn4Sb3 thermoelectric(TE) material β-Zn4Sb3 has the best performance during 350~400℃. Its advantages include low cost and simple fabricate process. Some researches indicated that its ZT value can reach 1.37 at 400℃ In this study, we select two methods to fabricate nano- and micro- grained Zn4Sb3 process. One is melt spinning process (30 m/s) for Zn4Sb3 ribbon and the other one is a traditional manufacture method by using melt diffusion and quenching for bulk sample. The melt spun ribbons and melt diffused bulk material were both grinded into powders, then mix these two powders with nano/micro-grain sized powder ratio of 95/5 vol.%、90/10 vol.%、85/15 vol.% and 80/20 vol.%. Then these mixed powders were fabricated into bulk samples via vacuum hot pressing (HP) method. The fracture toughness can reach as high as 1.46 MPa．m1/2 because of its high relative density above 99.5%. We propose that with nano- and micro- grained composite structure can increase the phonon scattering and decrease the lattice thermal conductivity at the same time and so as to enhance ZT value. The results show that the optima thermoelectric property occurs at the bulk sample with nano/micro-grain grained vol.ume ratio of 80/20, the measurement of the Seebeck coefficient, electric conductivity, and thermal conductivity are 213 μV/K, 337 S/cm and 7.53 mW/cmK2 ,respectively, which presented a ZT value as high as 1.22 at 598 K.
