Fe,Ni置換型方鈷礦熱電材料高溫高壓制備及性能研究
發(fā)布時間：2018-09-09 14:22
【摘要】：本論文采用高溫高壓技術制備出單元素、雙元素置換到方鈷礦Co Sb_3中Co位的熱電材料,并對其熱電性質進行了研究。重點研究了室溫下不同合成壓力對方鈷礦基熱電材料的電學輸運性能的影響,并對所合成樣品的相結構,微觀結構,熱電性能進行了測試以及分析。本論文的主要研究內容如下:(1)采用Ni元素進行單一置換,在1-3 GPa條件下成功制備出Ni_xCo_(4-x)Sb_(12)(x=0,0.025.0.1,0.15,0.25)材料。XRD測試結果表明:在合成壓力為1GPa時,制備出的樣品與標準Co Sb_3譜圖匹配良好。SEM電鏡照片表明樣品的晶粒均勻,晶界明顯。此外,樣品電學輸運性能測試結果表明:在制備壓力范圍內,樣品的Seebeck系數(shù)的絕對值與電阻率隨著合成壓力的增加趨于增加。合成壓力為1GPa時,樣品Ni_(0.15)Co_(3.85)Sb_(12)具有最優(yōu)功率因子為9′10-4Wm-1K-2。結果表明:相比純方鈷礦熱電材料,通過Ni元素替代到Co Sb_3的Co位后,電學性能得到顯著提高。隨后對該樣品進行中溫區(qū)熱電輸運性能相關測試及研究,結果表明:Ni元素替代到樣品中可以有效降低樣品的總熱導率。當合成壓力為1GPa時,溫度為600K時,樣品Ni_(0.15)Co_(3.85)Sb_(12)的最大品質因子ZT值為0.52。(2)采用雙元素Fe,Ni置換到Co位,用高溫高壓方法成功制備出Fe_yNi_(0.15)Co_(3.85-y)Sb_(12)(y=0.2,0.25,0.3)材料。在合成壓力范圍內,隨著合成壓力的增加,Seebeck系數(shù)的絕對值和電阻率都有所增;1GPa下合成的Fe0.2Ni0.1 5Co3.6 5Sb1 2樣品具有室溫下的最大功率因子為4.85′10-4Wm-1K-2,隨后對該樣品進行變溫熱電輸運性能的相關測試,結果表明:Fe,Ni雙元素置換到樣品中可有效降低樣品的晶格熱導率,在溫度為700K時,最優(yōu)品質因子ZT值為0.35。綜上所述,采用高溫高壓制備方法,同時通過元素置換到方鈷礦的鈷位時,能夠有效地改善材料的微觀結構;優(yōu)化材料的載流子濃度;造成明顯的微觀缺陷,以至于促進了聲子散射,降低了材料的晶格熱導率;最終實現(xiàn)優(yōu)化材料的熱電性能,提高了材料的ZT值。
[Abstract]:In this paper, the thermoelectric materials with single element and double element replacement to Co site in Co Sb_3 were prepared by high temperature and high pressure technique, and their thermoelectric properties were studied. The effect of different synthetic pressures on the electrical transport properties of the pyroelectric materials based on galactic cobalt was studied. The phase structure, microstructure and thermoelectric properties of the synthesized samples were tested and analyzed. The main research contents of this thesis are as follows: (1) Ni_xCo_ (4-x) Sb_ _ (12) (x _ (0) O _ (0) 0. 025.0.1 ~ 0.150.25) Ni_xCo_ (4-x) Sb_ _ (12) material was successfully prepared by single substitution of Ni elements under 1-3 GPa. The results show that: when the synthesis pressure is 1GPa, The prepared samples matched well with the standard Co Sb_3 spectra. The SEM electron microscope photos showed that the grain size of the samples was uniform and the grain boundary was obvious. In addition, the electrical transport properties of the samples show that the absolute value of the Seebeck coefficient and the resistivity of the samples tend to increase with the increase of the synthetic pressure in the range of preparation pressure. When the synthetic pressure is 1GPa, the sample Ni_ (0.15) Co_ (3.85) Sb_ (12) has an optimal power factor of 9 ~ (10 ~ (-4) Wm ~ (-1) K ~ (-2). The results show that the electrical properties of Co Sb_3 are improved significantly after the substitution of Ni element to the Co site of Co Sb_3 compared with pure cobalt ore thermoelectric materials. The thermoelectric transport properties of the sample were measured and studied at moderate temperature. The results show that the substitution of the element of Ni with the sample can effectively reduce the total thermal conductivity of the sample. The maximum quality factor ZT value of Ni_ (0.15) Co_ (3.85) Sb_ (12) was 0.52when the synthesis pressure was 1GPa and the temperature was 600K. (2) Fe_yNi_ (0.15) Co_ (3.85-y) Sb_ (12) (y0.20.250.30) was successfully prepared by high-temperature and high-pressure method. In the range of synthetic pressure, With the increase of synthetic pressure, the absolute value and resistivity of Seebeck coefficient increase. The Fe0.2Ni0.1 5Co3.6 5Sb1 _ 2 sample synthesized at 1 GPA has a maximum power factor of 4.85 脳 10 ~ (-4) W ~ (-1) K ~ (-2) at room temperature. The results show that the lattice thermal conductivity of the samples can be effectively reduced by the substitution of the two elements, and the ZT value of the optimal quality factor is 0.35 at 700K. To sum up, the preparation method of high temperature and high pressure, at the same time, when the elements are replaced to the cobalt site of the galactic ore, can effectively improve the microstructure of the material, optimize the carrier concentration of the material, and cause obvious microscopic defects. Thus the phonon scattering is promoted and the lattice thermal conductivity is reduced. Finally the thermoelectric properties of the material are optimized and the ZT value of the material is improved.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB34
[Abstract]:In this paper, the thermoelectric materials with single element and double element replacement to Co site in Co Sb_3 were prepared by high temperature and high pressure technique, and their thermoelectric properties were studied. The effect of different synthetic pressures on the electrical transport properties of the pyroelectric materials based on galactic cobalt was studied. The phase structure, microstructure and thermoelectric properties of the synthesized samples were tested and analyzed. The main research contents of this thesis are as follows: (1) Ni_xCo_ (4-x) Sb_ _ (12) (x _ (0) O _ (0) 0. 025.0.1 ~ 0.150.25) Ni_xCo_ (4-x) Sb_ _ (12) material was successfully prepared by single substitution of Ni elements under 1-3 GPa. The results show that: when the synthesis pressure is 1GPa, The prepared samples matched well with the standard Co Sb_3 spectra. The SEM electron microscope photos showed that the grain size of the samples was uniform and the grain boundary was obvious. In addition, the electrical transport properties of the samples show that the absolute value of the Seebeck coefficient and the resistivity of the samples tend to increase with the increase of the synthetic pressure in the range of preparation pressure. When the synthetic pressure is 1GPa, the sample Ni_ (0.15) Co_ (3.85) Sb_ (12) has an optimal power factor of 9 ~ (10 ~ (-4) Wm ~ (-1) K ~ (-2). The results show that the electrical properties of Co Sb_3 are improved significantly after the substitution of Ni element to the Co site of Co Sb_3 compared with pure cobalt ore thermoelectric materials. The thermoelectric transport properties of the sample were measured and studied at moderate temperature. The results show that the substitution of the element of Ni with the sample can effectively reduce the total thermal conductivity of the sample. The maximum quality factor ZT value of Ni_ (0.15) Co_ (3.85) Sb_ (12) was 0.52when the synthesis pressure was 1GPa and the temperature was 600K. (2) Fe_yNi_ (0.15) Co_ (3.85-y) Sb_ (12) (y0.20.250.30) was successfully prepared by high-temperature and high-pressure method. In the range of synthetic pressure, With the increase of synthetic pressure, the absolute value and resistivity of Seebeck coefficient increase. The Fe0.2Ni0.1 5Co3.6 5Sb1 _ 2 sample synthesized at 1 GPA has a maximum power factor of 4.85 脳 10 ~ (-4) W ~ (-1) K ~ (-2) at room temperature. The results show that the lattice thermal conductivity of the samples can be effectively reduced by the substitution of the two elements, and the ZT value of the optimal quality factor is 0.35 at 700K. To sum up, the preparation method of high temperature and high pressure, at the same time, when the elements are replaced to the cobalt site of the galactic ore, can effectively improve the microstructure of the material, optimize the carrier concentration of the material, and cause obvious microscopic defects. Thus the phonon scattering is promoted and the lattice thermal conductivity is reduced. Finally the thermoelectric properties of the material are optimized and the ZT value of the material is improved.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB34
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