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High pressure and high temperature to explore synthetic β-FeSi_2 thermoelectric materials

Author: MaYanPing
Tutor: ZhengYouJin；PengHongYan
School: Mudanjiang Teachers College
Course: Condensed Matter Physics
Keywords: High temperature and pressure β-FeSi2 Resistivity Seebeck coefficient
CLC: TN304.2
Type: Master's thesis
Year: 2011
Downloads: 18
Quote: 0
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Abstract


In this thesis, high-purity Fe and Si powders non-stoichiometric mixed on top of the press in the domestic six-sided , high-temperature and high-pressure synthesis . The main conclusions are as follows : pressure 3.5 GPa , the temperature of 800 ℃ alloy by Si single mass and ε - FeSi α - FeSi - 2 phase composition . Completely molten alloy not reached when the temperature at about 825 ℃ -925 ℃ this interval , the sample is mainly composed of ε- FeSi , α - FeSi 2 phase composition , silicon simple substance disappears , then silicon ferroalloy exist in a stable ε and α biphasic . Alloy when the temperature is greater than 950 ℃ to α - FeSi , 2 facies tetragonal α-FeSi 2 high temperature compounds in this system . The high solidification conditions , Fe-Si alloy under increasing pressure , in XRD mainly by ε - FeSi , α - FeSi in 2 phase composition , and no other phase change occurs ; With the increase in the synthesizing time alloy by pollution. After synthesis time , the investigation of the pressure , temperature , cubic press can not direct synthesis of β - FeSi 2 thermoelectric material . Undoped β-FeSi 2 for the P-type semiconductor material . Bulk samples on the synthesis of the press to 800 ° C at different times under an annealing treatment , and finally the β-FeSi 2 -phase samples . With under atmospheric pressure , and solidified under high pressure of Fe-Si eutectic structure after annealing treatment crystals contraction into island . By the resistivity of Co - doped synthetic samples , Seebeck coefficient seen from the power factor , the thermoelectric properties at room temperature the sample obtained is not high , taking into account the reported β-FeSi 2 for the high-temperature thermoelectric materials , so the variable temperature thermoelectric properties of the sample to be investigated. But compared to the undoped p - type β - FeSi 2 material , Seebeck coefficient have greatly improved resistivity than undoped reduced a lot. The doped Co synthetic samples with the initial performance of thermoelectric materials .

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Semiconductor technology > General issues > Material > Compound semiconductor
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