几种硫族化合物的制备、高压结构及热电性能研究
发布时间：2019-05-29 20:29
【摘要】：高压物理是研究物质在高压极端条件下的晶体结构、状态方程以及力学、电学和光学等特征的学科。在高压条件下发现很多物质具有不同于常压下的新结构、新性质和新规律,因此,高压技术为材料的制备和改性提供了一个重要的途径。在成员众多的硫族化合物中,由于其高压下丰富的物理性质以及广阔的应用前景,一直以来是科研工作者研究的热点。本论文利用高温高压方法制备了Bi Cu Ch O(Ch=S、Se、Te)、La Cu SO及Pb Se2五种硫族化合物;将高压技术与同步辐射、拉曼光谱测试相结合,对高压下Bi Cu Se O、Bi Cu SO、La Cu SO及Pb Se2的晶体结构进行了比较系统的研究;同时对Bi Cu Ch O(Ch=S、Se、Te)及Pb Se2的热电性能进行了测试和讨论,取得了一些比较有价值的研究结果。1、采用高温高压方法成功制备出四方相的Bi Cu Se O、Bi Cu SO、La Cu SO,对其拉曼特征峰进行了指认。并利用原位高压X射线衍射及原位高压拉曼手段对这三种铜硫族化合物在高压下结构的稳定性进行了系统的研究。结果如下:四方相的Bi Cu Se O、Bi Cu SO和La Cu SO,分别从13.97GPa、10.41GPa和11.64GPa开始,a轴出现负压缩率情形,c轴迅速减小,即体系发生了由四方相到塌缩四方相的等结构相变。经分析,这种压致等结构相变是与其晶体层状结构有关,在压力作用下其电荷存储层在ab面的剪切运动引起a轴的变大,其层与层之间共价键结合较弱,导致c轴特别容易被压缩。Bi Cu Se O及La Cu SO的高压拉曼结果显示在14.8GPa时出现新峰,及10.8GPa时各振动模式随压力变化斜率明显发生变化,与高压X光结果相一致。2、采用二次固相法制备出Bi Cu Se O前驱物,通过无压烧结和高压烧结方法制备出块体多晶材料。通过Rietveld精修和密度泛函理论计算表明高压能够抑制Bi Cu Se O本征缺陷的产生,因此高压烧结样品具有更高的霍尔迁移率和Seebeck系数。同时由于高压作用导致晶粒细化,进而得到较小的热导率。3、对高温高压合成的Bi Cu Ch O(Ch=S、Se、Te)样品进行了Rietveld精修及热电性能的测试。随着硫族元素Ch原子半径的增大,Bi Cu Ch O样品的导电活化能减小,Seebeck系数和电阻率减小,热导率降低。Bi Cu SO、Bi Cu Se O和Bi Cu Te O的最高品质因子在650K条件下分别达到了0.07,0.31,和0.65。4、利用高温高压方法合成了Bi Cu Se O-Bi Cu Te O固溶体,并对其微观形貌和热电性能进行了测试,结果发现富Se样品的粒度较小(1μm),富Te样品的层状结构更为明显。样品的电阻率和晶格热导率随着Te含量的增大逐渐减小,品质因子升高。5、成功利用机械合金化结合高温高压方法直接制备出四方相Pb Se2。原位高压X射线衍射研究表明Pb Se2从19.93GPa开始发生结构相变,利用结构检索的方法,确定其高压相为对称性较低的三斜相,在相变过程中体积塌缩了18.4%。通过理论计算表明,相变前后Pb Se2发生了半导体到金属的转变。6、对Pb Se2的热电性能进行了测试,通过电阻率,Seebeck系数及X光测试表明四方相Pb Se2在超过400K温度条件下会分解为立方相的Pb Se和Se。Pb Se2热导率远小于相同方法合成的立方相Pb Se,结合密度泛函理论计算的结果,Pb Se2极低的热导率是因为其原子间结合力较弱而化学键的非简谐性较强所致。
[Abstract]:The high-pressure physics is the study of the crystal structure, state equation and mechanics, electrical and optical characteristics of the material under the extreme conditions of high pressure. Under the condition of high pressure, many substances have the new structure, new property and new law which are different from the normal pressure. Therefore, the high-pressure technology provides an important way for the preparation and modification of the materials. It has been a hot point for researchers to study the rich physical properties and wide application prospects of its high pressure in a large number of chalcogenide compounds. In this paper, five sulfur family compounds of Bi Cu Ch O (Ch = S, Se, Te), La Cu SO and Pb Se2 are prepared by high-temperature and high-pressure process, and the high-voltage technology is combined with the synchronous radiation and the Raman spectrum test, and the Bi Cu Se O, Bi Cu SO, The crystal structure of La Cu SO and Pb Se2 was studied, and the thermoelectric properties of Bi Cu Ch O (Ch = S, Se, Te) and Pb Se2 were tested and discussed, and some valuable research results were obtained. The Raman characteristic peak of Bi Cu SO, La Cu SO was designated. The stability of these three kinds of copper-sulfur compounds under high pressure was studied by in-situ high-pressure X-ray diffraction and in-situ high-pressure Raman method. The results are as follows: Bi Cu Se O, Bi Cu SO and La Cu SO in the tetragonal phase start from 13.97 GPa, 10.41 GPa and 11.64 GPa, respectively. The result of the analysis shows that the phase transition of the piezoelectric material is related to the crystal layer structure. Under the action of the pressure, the shear movement of the charge storage layer in the ab surface causes the increase of a-axis, the covalent bond between the layer and the layer is weak, and the c-axis is particularly easy to be compressed. The results of the high-pressure Raman show of Bi Cu Se O and La Cu SO show that there is a new peak at 14.8 GPa, and the slope of each vibration mode with the pressure change is obviously changed at the time of 10.8 GPa, which is consistent with the high-pressure X-ray results. The bulk polycrystalline material is prepared by pressureless sintering and high-pressure sintering. The results of Rietveld refinement and density functional theory show that the high pressure can inhibit the generation of the intrinsic defects of Bi Cu Se O, so the high-voltage sintered samples have higher Hall mobility and Seebeck coefficient. At the same time, because of the high-pressure effect, the crystal grain is refined, and the smaller thermal conductivity is obtained. The test of Rietveld fine repair and thermoelectric property is carried out on the high-temperature and high-pressure synthesized Bi Cu Ch O (Ch = S, Se, Te) samples. With the increase of the atomic radius of the Ch atom of the chalcogen element, the conductive activation energy of the Bi Cu Ch O sample is reduced, the Seebeck coefficient and the resistivity are reduced, and the thermal conductivity is reduced. The highest quality factors of Bi Cu SO, Bi Cu Se O and Bi Cu Te O reach 0.07, 0.31, and 0.65.4 respectively under the condition of 650 K, and the Bi Cu Se O-Bi Cu Te O solid solution is synthesized by the high-temperature and high pressure method, and the micro-morphology and the thermal property of the Bi Cu Se O-Bi Cu Te O solid solution are tested. The results show that the particle size of the Se-rich sample is small (1. mu.m), and the layered structure of the Te-rich sample is more obvious. The resistivity of the sample and the thermal conductivity of the lattice are gradually reduced with the increase of Te content and the quality factor is increased.5, the tetragonal phase Pb Se2 is directly prepared by mechanical alloying in combination with the high-temperature and high-pressure method. The in-situ high-pressure X-ray diffraction study shows that the Pb Se2 has a structural phase change from 19.93 GPa, and the structure search method is used to determine the three-oblique phase with lower symmetry of the high-voltage phase, and the volume is collapsed by 18.4% in the phase-change process. It is shown by the theoretical calculation that the transition of the semiconductor to the metal occurs before and after the phase change.6. The thermal property of the Pb Se2 is tested and the resistivity is obtained. Seebeck coefficient and X-ray show that the thermal conductivity of Pb Se and Se. The low thermal conductivity of Pb Se2 is due to the weak binding force between the atoms and the non-simple harmonic of the chemical bond.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O521
[Abstract]:The high-pressure physics is the study of the crystal structure, state equation and mechanics, electrical and optical characteristics of the material under the extreme conditions of high pressure. Under the condition of high pressure, many substances have the new structure, new property and new law which are different from the normal pressure. Therefore, the high-pressure technology provides an important way for the preparation and modification of the materials. It has been a hot point for researchers to study the rich physical properties and wide application prospects of its high pressure in a large number of chalcogenide compounds. In this paper, five sulfur family compounds of Bi Cu Ch O (Ch = S, Se, Te), La Cu SO and Pb Se2 are prepared by high-temperature and high-pressure process, and the high-voltage technology is combined with the synchronous radiation and the Raman spectrum test, and the Bi Cu Se O, Bi Cu SO, The crystal structure of La Cu SO and Pb Se2 was studied, and the thermoelectric properties of Bi Cu Ch O (Ch = S, Se, Te) and Pb Se2 were tested and discussed, and some valuable research results were obtained. The Raman characteristic peak of Bi Cu SO, La Cu SO was designated. The stability of these three kinds of copper-sulfur compounds under high pressure was studied by in-situ high-pressure X-ray diffraction and in-situ high-pressure Raman method. The results are as follows: Bi Cu Se O, Bi Cu SO and La Cu SO in the tetragonal phase start from 13.97 GPa, 10.41 GPa and 11.64 GPa, respectively. The result of the analysis shows that the phase transition of the piezoelectric material is related to the crystal layer structure. Under the action of the pressure, the shear movement of the charge storage layer in the ab surface causes the increase of a-axis, the covalent bond between the layer and the layer is weak, and the c-axis is particularly easy to be compressed. The results of the high-pressure Raman show of Bi Cu Se O and La Cu SO show that there is a new peak at 14.8 GPa, and the slope of each vibration mode with the pressure change is obviously changed at the time of 10.8 GPa, which is consistent with the high-pressure X-ray results. The bulk polycrystalline material is prepared by pressureless sintering and high-pressure sintering. The results of Rietveld refinement and density functional theory show that the high pressure can inhibit the generation of the intrinsic defects of Bi Cu Se O, so the high-voltage sintered samples have higher Hall mobility and Seebeck coefficient. At the same time, because of the high-pressure effect, the crystal grain is refined, and the smaller thermal conductivity is obtained. The test of Rietveld fine repair and thermoelectric property is carried out on the high-temperature and high-pressure synthesized Bi Cu Ch O (Ch = S, Se, Te) samples. With the increase of the atomic radius of the Ch atom of the chalcogen element, the conductive activation energy of the Bi Cu Ch O sample is reduced, the Seebeck coefficient and the resistivity are reduced, and the thermal conductivity is reduced. The highest quality factors of Bi Cu SO, Bi Cu Se O and Bi Cu Te O reach 0.07, 0.31, and 0.65.4 respectively under the condition of 650 K, and the Bi Cu Se O-Bi Cu Te O solid solution is synthesized by the high-temperature and high pressure method, and the micro-morphology and the thermal property of the Bi Cu Se O-Bi Cu Te O solid solution are tested. The results show that the particle size of the Se-rich sample is small (1. mu.m), and the layered structure of the Te-rich sample is more obvious. The resistivity of the sample and the thermal conductivity of the lattice are gradually reduced with the increase of Te content and the quality factor is increased.5, the tetragonal phase Pb Se2 is directly prepared by mechanical alloying in combination with the high-temperature and high-pressure method. The in-situ high-pressure X-ray diffraction study shows that the Pb Se2 has a structural phase change from 19.93 GPa, and the structure search method is used to determine the three-oblique phase with lower symmetry of the high-voltage phase, and the volume is collapsed by 18.4% in the phase-change process. It is shown by the theoretical calculation that the transition of the semiconductor to the metal occurs before and after the phase change.6. The thermal property of the Pb Se2 is tested and the resistivity is obtained. Seebeck coefficient and X-ray show that the thermal conductivity of Pb Se and Se. The low thermal conductivity of Pb Se2 is due to the weak binding force between the atoms and the non-simple harmonic of the chemical bond.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O521
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