(Fe0.98Mn0.02)xSi2(x≤1) 조성으로, 용융법으로 제조한 α-Fe2Si5상의 잉곳을 730~850˚C에서 4~20시간 열처리하거나, 기계적 합금화로 제조한 ε-FeSi과 Si상으로 구성된 분말을 760~850˚C에서 10분간 가압통전소결하므로써 β-FeSi2기지상에 Si이 분산된 미세조직을 얻을 수 있었다. 조성, 열처리 온도와 소결 온도에 따라 Si 분상의 크기와 간격이 각기 0.05~0.27μm와 0.2~0.6μm 범위에서 변화하였다. 이와 같은 Si 분산상에 의해 β-FeSi2의 격자 열전도도가 감소되어 성능지수가 향상될 수 있을 것으로 기대된다.
A new process using rapid solidification (melt spinning method) followed by pressing and sintering was investigated to produce the n-type thermoelectric ribbons of 90% +10% doped with . Quenched ribbons are very brittle and consisted of homogeneous pseudo-binary solid solutions. Property variations of the materials was investigated as a function of variables, such as dopant quantity and sintering temperature. When the process parameters were optimized, the maximum figure of merit was .
금속분말 Fe와 Si에 KNO3(Fe+Si)무게비=0.2로 점화촉매 KNO3를 혼합하고 50MPa로 성형한 후 점화시키는 비기체연소합성(SHS; Self propagating High temperature Synthesis)법으로 출발 분말을 얻었다. 점화분위기를 공기 및 Ar으로 한 경우 XRD결과에서 특별한 차이가 없었고 두 경우 모두 SiO2피크가 검출되었다. 합성된 분말을 성형한 후 1190˚C환원분위기에서 소결하고 포석온도이하에서 열처리하여 반도성 FeSi2가 주상인 Fe-Si계 열전재료를 제조하였다. Fe/Si무게비=46/54,44/56 및 42/58시편의 제벡계수는 Si함량이 증가할수록 증가하였다. 점화후의 세척처리를 2단계로 하는 경우 제벡계수의 부호가 변화하여 p-type에서 n-type으로 변화하며 소결밀도가 크게 상승하였다. 조성에 관계없이 공통적으로 발견되는 SiO2는 점화시의 분위기보다는 점화촉매에 포함된 K성분이 소결 및 열처리시 산화제로 작용하여 형성되는 것이 확인되었다.
The efficiency of thermoelectric devices for different applications is known to depend on the thermoelectric effectiveness of the material which tends to grow with the increase of its chemical homogeneity. Thus an important goal for thermal devices is to obtain chemically homogeneous solid solutions. In this work, the new process with rapid solidification (melt spinning method) followed by hot pressing was investigated to produce homogeneous material. Characteristics of the material were examined with HRD, SEM, EPMA-line scan and bending test. Property variations of the materials were investigated as a function of variables, such as dopant quantity and hot pressing temperature. Quenched ribbons are very brittle and consist of homogeneous , solid solutions. When the process parameters were optimized, the maximum figure of merit was 2.038×10-3K-4. The bending strength of the material hot pressed at 50 was 8.2 kgf/.
solid solutions are of great interest as materials for thermoelectric energy conversion. One of the key technologies to ensure the efficiency of thermoelectric device is to obtain chemically homogeneous solid solutions. In this work, the new process with rapid solidification followed by hot pressing was investigated to produce homogeneous thermoelectric materials. Characteristics of the materials were examined with XRD, SEM, EPMA-line scan and bending test. Property variations of the materials were investigated as a function of variables, such as excess Te quantity and hot pressing temperature. Quenched ribbons are very brittle and consisted of homogeneous , solid solutions. When the process parameters were optimized, the maximum figure of merit was 3.073. The bending strength of the material, hot pressed at 45, was 5.87 kgf/.