掺杂的笼状材料的制备及其热电性能的研究
发布时间：2018-09-05 09:07
【摘要】：热电材料是一种能实现电能和热能之间相互转换的功能材料。具有笼子结构的Co Sb3型和基于Ba-Ge的Ⅰ型clathrate笼状热电材料有着“声子玻璃-电子晶体”特征,它们可以实现电热性能的独立调控。研究表明,掺杂或填充是降低晶格热导率,从而提高热电性能的重要手段。本文通过高压的方法合成了掺杂或填充型的具有高热电性能的笼状热电材料。以高纯的相应单质元素为原料,采用高压合成与放电等离子烧结相结合的方法制备样品。采用X射线衍射、扫描电子显微镜、拉曼散射光谱及PPMS系统等分析样品的组成成分、结构及载流子浓度。采用ZEM-3测量样品的电阻率及塞贝克系数。采用TC9000H测量样品的电导率。1、按照化学计量CoSb3-xSex(x=0.05,0.1,0.2,0.3)和CoSb2.85-yTe0.15Sey(y=0.025,0.05,0.1)合成了两组Co Sb3基样品。高压的方法使在常压条件下不能掺杂进的Se掺进了Co Sb3的晶格骨架位置,并且在高压5GPa的条件下Se的最大掺杂分数可达3%。对于样品x=0.3的热导率?在整个的温度范围内都低于1.83 W/Km。高压下Se/Te的共掺杂量也较常压下有一定提高。样品y=0.5的ZT值在780K时可高达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系统的I型笼状物样品。X射线衍射表明它们是单相的样品,但背散射电子成像却表明它们有两种第2相。面扫描成像表明Ce均匀地分布于基体相和第2相中。得到的样品为有Ce填充晶格孔洞的但含有第二相的I型笼状物。Ce含量的提高明显增加了样品的ZT值。样品Ce1.2Ba7.0Ni0.44Al13.8Ge31.76在900K时的ZT值可达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系统的一组样品。X射线表明得到的样品为单相样品。EDS表明x=0.3与x=0.5样品的中Yb的填充量分别为0.21与0.32。然而,含有Yb的样品中均含有少量Yb2O3杂相,这可能跟Yb的氧化无法避免有关。x=0.3的样品的热导率在800K时可低至1.23W/Km,这使得它的ZT值可达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.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34
本文编号：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.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34
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