Enhanced thermoelectric and mechanical performance of polycrystalline p-type Bi_0.5Sb_1.5Te₃ by a traditional physical metallurgical strategy

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• 作者：Ye Xiao ; Junyou Yang ; ^{jyyang@mail.hust.edu.cn" class="auth_mail} ; ^{Junyou.YANG@163.com" class="auth_mail} ; Gen Li ; Ming Liu ; Liangwei Fu ; Yubo Luo ; Weixin Li ; Jiangying Peng
• 关键词：A. Ternary alloy systems ; B. Thermoelectric properties ; B. Mechanical properties at ambient temperature ; C. Melting ; D. Microstructure
• 刊名：Intermetallics
• 出版年：July, 2014
• 年：2014
• 卷：50
• 期：Complete
• 页码：20-27
• 全文大小：2107 K

文摘

In this paper, p-type Bi_0.5Sb_1.5Te₃ polycrystalline materials have been fabricated by a traditional vacuum melting method, and the effects of cooling rate and MoSi₂ addition on the microstructure, thermoelectric and mechanical performance of the polycrystalline materials have been studied detailedly. It shows that the amount of Te-rich eutectic phase increases and the lamellar microstructure has been refined with the increase of the cooling rate. Due to the combined effect of cooling rate on the carrier concentration and mobility, the air cooled sample has higher figure of merit than the furnace cooled, water cooled and liquid nitrogen cooled samples, and a maximal ZT of 1.02 at 50聽掳C was obtained for the air cooled polycrystalline sample. Under the same air cooling condition, the inhomogeneous nucleation sites increase with increasing the amount of MoSi₂ particles, therefore the amount of Te-rich eutectic phase increases and the lamellar microstructure get refined, and the thermal conductivity of the sample decreases significantly due to the extra phonon scattering by the refined microstructure and MoSi₂ particles. The resulted figure of merit ZT increases with increasing the amount of MoSi₂ particles, and it decreases with further increasing the MoSi₂ content after attaining the vertex of ZT聽=聽1.33 at 100聽掳C at a content of 0.2聽wt.% MoSi₂. The flexural strength of the air cooled polycrystalline sample also increases with the amount of MoSi₂ increasing from 0 to 0.3聽wt.%, and a nearly 56% enhancement was achieved for the 0.2聽wt.% MoSi₂ sample (28.0聽MPa) compared with the MoSi₂ free sample. The improvement of flexural strength is in agreement with the Hall-Petch strengthening mechanism due to the lamellar microstructure refinement induced by MoSi₂.