幾種硫族化合物的制備、高壓結(jié)構(gòu)及熱電性能研究
發(fā)布時間：2019-05-29 20:29
【摘要】：高壓物理是研究物質(zhì)在高壓極端條件下的晶體結(jié)構(gòu)、狀態(tài)方程以及力學(xué)、電學(xué)和光學(xué)等特征的學(xué)科。在高壓條件下發(fā)現(xiàn)很多物質(zhì)具有不同于常壓下的新結(jié)構(gòu)、新性質(zhì)和新規(guī)律,因此,高壓技術(shù)為材料的制備和改性提供了一個重要的途徑。在成員眾多的硫族化合物中,由于其高壓下豐富的物理性質(zhì)以及廣闊的應(yīng)用前景,一直以來是科研工作者研究的熱點。本論文利用高溫高壓方法制備了Bi Cu Ch O(Ch=S、Se、Te)、La Cu SO及Pb Se2五種硫族化合物;將高壓技術(shù)與同步輻射、拉曼光譜測試相結(jié)合,對高壓下Bi Cu Se O、Bi Cu SO、La Cu SO及Pb Se2的晶體結(jié)構(gòu)進行了比較系統(tǒng)的研究;同時對Bi Cu Ch O(Ch=S、Se、Te)及Pb Se2的熱電性能進行了測試和討論,取得了一些比較有價值的研究結(jié)果。1、采用高溫高壓方法成功制備出四方相的Bi Cu Se O、Bi Cu SO、La Cu SO,對其拉曼特征峰進行了指認。并利用原位高壓X射線衍射及原位高壓拉曼手段對這三種銅硫族化合物在高壓下結(jié)構(gòu)的穩(wěn)定性進行了系統(tǒng)的研究。結(jié)果如下:四方相的Bi Cu Se O、Bi Cu SO和La Cu SO,分別從13.97GPa、10.41GPa和11.64GPa開始,a軸出現(xiàn)負壓縮率情形,c軸迅速減小,即體系發(fā)生了由四方相到塌縮四方相的等結(jié)構(gòu)相變。經(jīng)分析,這種壓致等結(jié)構(gòu)相變是與其晶體層狀結(jié)構(gòu)有關(guān),在壓力作用下其電荷存儲層在ab面的剪切運動引起a軸的變大,其層與層之間共價鍵結(jié)合較弱,導(dǎo)致c軸特別容易被壓縮。Bi Cu Se O及La Cu SO的高壓拉曼結(jié)果顯示在14.8GPa時出現(xiàn)新峰,及10.8GPa時各振動模式隨壓力變化斜率明顯發(fā)生變化,與高壓X光結(jié)果相一致。2、采用二次固相法制備出Bi Cu Se O前驅(qū)物,通過無壓燒結(jié)和高壓燒結(jié)方法制備出塊體多晶材料。通過Rietveld精修和密度泛函理論計算表明高壓能夠抑制Bi Cu Se O本征缺陷的產(chǎn)生,因此高壓燒結(jié)樣品具有更高的霍爾遷移率和Seebeck系數(shù)。同時由于高壓作用導(dǎo)致晶粒細化,進而得到較小的熱導(dǎo)率。3、對高溫高壓合成的Bi Cu Ch O(Ch=S、Se、Te)樣品進行了Rietveld精修及熱電性能的測試。隨著硫族元素Ch原子半徑的增大,Bi Cu Ch O樣品的導(dǎo)電活化能減小,Seebeck系數(shù)和電阻率減小,熱導(dǎo)率降低。Bi Cu SO、Bi Cu Se O和Bi Cu Te O的最高品質(zhì)因子在650K條件下分別達到了0.07,0.31,和0.65。4、利用高溫高壓方法合成了Bi Cu Se O-Bi Cu Te O固溶體,并對其微觀形貌和熱電性能進行了測試,結(jié)果發(fā)現(xiàn)富Se樣品的粒度較小(1μm),富Te樣品的層狀結(jié)構(gòu)更為明顯。樣品的電阻率和晶格熱導(dǎo)率隨著Te含量的增大逐漸減小,品質(zhì)因子升高。5、成功利用機械合金化結(jié)合高溫高壓方法直接制備出四方相Pb Se2。原位高壓X射線衍射研究表明Pb Se2從19.93GPa開始發(fā)生結(jié)構(gòu)相變,利用結(jié)構(gòu)檢索的方法,確定其高壓相為對稱性較低的三斜相,在相變過程中體積塌縮了18.4%。通過理論計算表明,相變前后Pb Se2發(fā)生了半導(dǎo)體到金屬的轉(zhuǎn)變。6、對Pb Se2的熱電性能進行了測試,通過電阻率,Seebeck系數(shù)及X光測試表明四方相Pb Se2在超過400K溫度條件下會分解為立方相的Pb Se和Se。Pb Se2熱導(dǎo)率遠小于相同方法合成的立方相Pb Se,結(jié)合密度泛函理論計算的結(jié)果,Pb Se2極低的熱導(dǎo)率是因為其原子間結(jié)合力較弱而化學(xué)鍵的非簡諧性較強所致。
[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.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：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.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O521
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