摻雜的籠狀材料的制備及其熱電性能的研究
發(fā)布時間：2018-09-05 09:07
【摘要】：熱電材料是一種能實現(xiàn)電能和熱能之間相互轉(zhuǎn)換的功能材料。具有籠子結(jié)構(gòu)的Co Sb3型和基于Ba-Ge的Ⅰ型clathrate籠狀熱電材料有著“聲子玻璃-電子晶體”特征,它們可以實現(xiàn)電熱性能的獨立調(diào)控。研究表明,摻雜或填充是降低晶格熱導(dǎo)率,從而提高熱電性能的重要手段。本文通過高壓的方法合成了摻雜或填充型的具有高熱電性能的籠狀熱電材料。以高純的相應(yīng)單質(zhì)元素為原料,采用高壓合成與放電等離子燒結(jié)相結(jié)合的方法制備樣品。采用X射線衍射、掃描電子顯微鏡、拉曼散射光譜及PPMS系統(tǒng)等分析樣品的組成成分、結(jié)構(gòu)及載流子濃度。采用ZEM-3測量樣品的電阻率及塞貝克系數(shù)。采用TC9000H測量樣品的電導(dǎo)率。1、按照化學計量CoSb3-xSex(x=0.05,0.1,0.2,0.3)和CoSb2.85-yTe0.15Sey(y=0.025,0.05,0.1)合成了兩組Co Sb3基樣品。高壓的方法使在常壓條件下不能摻雜進的Se摻進了Co Sb3的晶格骨架位置,并且在高壓5GPa的條件下Se的最大摻雜分數(shù)可達3%。對于樣品x=0.3的熱導(dǎo)率?在整個的溫度范圍內(nèi)都低于1.83 W/Km。高壓下Se/Te的共摻雜量也較常壓下有一定提高。樣品y=0.5的ZT值在780K時可高達1.29。2、按照CexBa8.2-xNi0.62Al13.8Ge31.58(x=0.5,1.2)和Ce1.2Ba7.0Ni0.44Al13.8Ge31.76合成了基于Ba-Al-Ge系統(tǒng)的I型籠狀物樣品。X射線衍射表明它們是單相的樣品,但背散射電子成像卻表明它們有兩種第2相。面掃描成像表明Ce均勻地分布于基體相和第2相中。得到的樣品為有Ce填充晶格孔洞的但含有第二相的I型籠狀物。Ce含量的提高明顯增加了樣品的ZT值。樣品Ce1.2Ba7.0Ni0.44Al13.8Ge31.76在900K時的ZT值可達0.26。3、按照Ba8-xYbx Ni0.1Zn0.54Ga13.8Ge31.56(x=0、0.1、0.3及0.5)合成了基于Ba-Ga-Ge系統(tǒng)的一組樣品。X射線表明得到的樣品為單相樣品。EDS表明x=0.3與x=0.5樣品的中Yb的填充量分別為0.21與0.32。然而,含有Yb的樣品中均含有少量Yb2O3雜相,這可能跟Yb的氧化無法避免有關(guān)。x=0.3的樣品的熱導(dǎo)率在800K時可低至1.23W/Km,這使得它的ZT值可達0.91。
[Abstract]:Thermoelectric material is a kind of functional material which can realize the conversion between electric energy and heat energy. Co Sb3 type with cage structure and type I clathrate cage thermoelectric material based on Ba-Ge have the characteristics of "phonon glass-electron crystal", which can realize the independent regulation of electrothermal properties. It is shown that doping or filling is an important means to decrease the lattice thermal conductivity and improve the thermoelectric properties. In this paper, the high voltage method is used to synthesize the caged thermoelectric materials with high thermoelectric properties. The samples were prepared by high pressure synthesis and spark plasma sintering (SPS). The composition, structure and carrier concentration of the samples were analyzed by X-ray diffraction, scanning electron microscopy, Raman scattering spectroscopy and PPMS system. The resistivity and Seebeck coefficient of the samples were measured by ZEM-3. Two groups of Co Sb3 based samples were synthesized according to stoichiometric CoSb3-xSex and CoSb2.85-yTe0.15Sey (yttrium 0.025 0. 05% 0. 05%) by using TC9000H to measure the electrical conductivity of the samples. The method of high pressure makes the Se that can't be doped into the lattice skeleton position of Co Sb3 under normal pressure, and the maximum doping fraction of Se can reach 3% under the condition of high pressure 5GPa. For the thermal conductivity of sample x0. 3? In the whole temperature range, the temperature is lower than 1.83 W / Km. The co-doping amount of Se/Te at high pressure is also higher than that at normal pressure. The ZT value of sample yt0. 5 can reach 1. 29.2at 780K. According to CexBa8.2-xNi0.62Al13.8Ge31.58 (XY 0. 5N. 2) and Ce1.2Ba7.0Ni0.44Al13.8Ge31.76, the sample of type I cage based on Ba-Al-Ge system. X-ray diffraction shows that they are single phase samples, but the back scattering electron imaging shows that they have two kinds of second phase. Surface scanning imaging shows that Ce is uniformly distributed in the matrix and the second phase. The increase of the content of type I cage. Ce with Ce filled lattice cavity but containing the second phase obviously increased the ZT value of the sample. The ZT value of sample Ce1.2Ba7.0Ni0.44Al13.8Ge31.76 can reach 0.26.3 at 900K. According to the Ba8-xYbx Ni0.1Zn0.54Ga13.8Ge31.56 (x0. 0. 1 + 0. 3 and 0. 5), a group of samples based on Ba-Ga-Ge system. X ray shows that the sample is a single phase sample. EDS shows that the filling amount of Yb in xn0. 3 and X0. 5 samples is 0. 21 and 0. 32, respectively. However, a small amount of Yb2O3 heterophase is found in all samples containing Yb, which may be related to the oxidation of Yb. The thermal conductivity of the sample with Yb is as low as 1.23 W / Km at 800K, which leads to the ZT value of 0.91.
【學位授予單位】：燕山大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB34
本文編號：2223828
[Abstract]:Thermoelectric material is a kind of functional material which can realize the conversion between electric energy and heat energy. Co Sb3 type with cage structure and type I clathrate cage thermoelectric material based on Ba-Ge have the characteristics of "phonon glass-electron crystal", which can realize the independent regulation of electrothermal properties. It is shown that doping or filling is an important means to decrease the lattice thermal conductivity and improve the thermoelectric properties. In this paper, the high voltage method is used to synthesize the caged thermoelectric materials with high thermoelectric properties. The samples were prepared by high pressure synthesis and spark plasma sintering (SPS). The composition, structure and carrier concentration of the samples were analyzed by X-ray diffraction, scanning electron microscopy, Raman scattering spectroscopy and PPMS system. The resistivity and Seebeck coefficient of the samples were measured by ZEM-3. Two groups of Co Sb3 based samples were synthesized according to stoichiometric CoSb3-xSex and CoSb2.85-yTe0.15Sey (yttrium 0.025 0. 05% 0. 05%) by using TC9000H to measure the electrical conductivity of the samples. The method of high pressure makes the Se that can't be doped into the lattice skeleton position of Co Sb3 under normal pressure, and the maximum doping fraction of Se can reach 3% under the condition of high pressure 5GPa. For the thermal conductivity of sample x0. 3? In the whole temperature range, the temperature is lower than 1.83 W / Km. The co-doping amount of Se/Te at high pressure is also higher than that at normal pressure. The ZT value of sample yt0. 5 can reach 1. 29.2at 780K. According to CexBa8.2-xNi0.62Al13.8Ge31.58 (XY 0. 5N. 2) and Ce1.2Ba7.0Ni0.44Al13.8Ge31.76, the sample of type I cage based on Ba-Al-Ge system. X-ray diffraction shows that they are single phase samples, but the back scattering electron imaging shows that they have two kinds of second phase. Surface scanning imaging shows that Ce is uniformly distributed in the matrix and the second phase. The increase of the content of type I cage. Ce with Ce filled lattice cavity but containing the second phase obviously increased the ZT value of the sample. The ZT value of sample Ce1.2Ba7.0Ni0.44Al13.8Ge31.76 can reach 0.26.3 at 900K. According to the Ba8-xYbx Ni0.1Zn0.54Ga13.8Ge31.56 (x0. 0. 1 + 0. 3 and 0. 5), a group of samples based on Ba-Ga-Ge system. X ray shows that the sample is a single phase sample. EDS shows that the filling amount of Yb in xn0. 3 and X0. 5 samples is 0. 21 and 0. 32, respectively. However, a small amount of Yb2O3 heterophase is found in all samples containing Yb, which may be related to the oxidation of Yb. The thermal conductivity of the sample with Yb is as low as 1.23 W / Km at 800K, which leads to the ZT value of 0.91.
【學位授予單位】：燕山大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB34
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