Al-Ir 系近似結晶の高圧合成を用いた原子欠損制御による熱電特性向上
2020 年 16 巻 3 号 p. 139-143
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2020 年 16 巻 3 号 p. 139-143
Although the binary Al-Ir cubic quasicrystalline approximant (QCA) has been expected to be a narrow gap semiconductor， it does not realize due to large amount of aluminum sites vacancies leading to excess hole doping. We suggest that a high-pressure synthesis (HPS) is effective to reduce vacancies. In this work, effects of HPS on structural and thermoelectric properties were investigated for an Al-Ir QCA. We found that the Seebeck coefficient of a sample made by HPS has a larger value compared to that sintered by using conventional spark plasma sintering (SPS). Further， the lattice constant and the analyzed aluminum composition increased as high pressure applied due to increasing the number of Al atoms in the Ir-12 icosahedral cluster. These results indicate that HPS suppressed vacancies in the cluster leading to a 2 times higher value of zT.
