Bi-Te is a thermoelectric material used at room temperature. It is typically fabricated as a single-crystal ingot, making processing difficult and material loss very high. Pressureless sintering processes have been studied to address these issues; however, they typically result in lower-density material. Methods such as hot isostatic pressing and spark plasma sintering have mainly been studied. However, there has been limited research on pressureless sintering without additional steps such as pressurization or charging. The aim of this study is to obtain a dense Bi₂Te_2.7Se_0.3 sintered body by combining rapid sintering with air sintering by modifying a typical sintering furnace. The effect of heating rate on densification and phase change was also investigated. Bi₂Te_2.7Se_0.3 powder was first synthesized by the mechanochemical method. The synthesized powder was then heated at a rate of 5°C/s to 20°C/s and finally sintered at a temperature of 570°C for 10 min in H₂/N₂ mixture under Te-rich conditions. These conditions produced a sintered body with relative density of at least 90% of the theoretical density, and a bulk density of 6.98 g/cm³ was obtained when temperature was increased at a rate of 20°C/s. Observation of the microstructure showed that porosity decreased as the heating rate was increased. The results of this study confirm that the heating rate during rapid sintering can affect the density of the sintered body.

中文翻译：

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加热速率对Bi 2 Te 2.7 Se 0.3烧结体密度和显微组织的影响

Bi-Te是在室温下使用的热电材料。它通常被制造为单晶锭，使得加工困难并且材料损失非常高。为了解决这些问题，已经研究了无压烧结工艺。但是，它们通常会导致密度较低的材料。主要研究了热等静压和火花等离子体烧结等方法。但是，对于无压烧结的研究还很有限，没有其他步骤，例如加压或装料。这项研究的目的是获得致密的Bi ₂ Te _2.7 Se _0.3通过改进典型的烧结炉，将快速烧结与空气烧结相结合，形成烧结体。还研究了加热速率对致密化和相变的影响。首先通过机械化学方法合成了Bi ₂ Te _2.7 Se _0.3粉末。然后将合成粉末以5°C / s的速率加热到20°C / s，最后在富含Te的条件下在H ₂ / N ₂混合物中以570°C的温度烧结10分钟。这些条件产生的烧结体的相对密度至少为理论密度的90％，堆积密度为6.98 g / cm ^3。当以20℃/ s的速率升高温度时，获得了α-β-烯烃。显微组织的观察表明，孔隙率随加热速率的增加而降低。这项研究的结果证实了快速烧结过程中的加热速率会影响烧结体的密度。