叠氮化铵以及碱土金属叠氮化物的高压研究

发布时间：2019-06-04 11:38

【摘要】：本论文采用原位高压同步辐射X射线衍射、原位高压拉曼散射光谱和原位高压红外吸收光谱等多种高压实验技术，利用金刚石对顶砧准静水压高压实验装置，对叠氮化铵以及碱土金属叠氮化物进行了高压结构相变以及结构稳定性的研究。通过一系列高压实验，发现了多个高压新相。并总结归纳出了碱土金属叠氮化物高压下的相变规律。 1.在常温条件下，对叠氮化铵（NH4N3）进行了原位高压同步辐射X射线衍射光谱、原位高压拉曼光谱以及原位高压红外吸收光谱的研究。实验所达到的最高压力分别为50.5GPa、22.4GPa和20GPa。由于叠氮根离子的取向性，正交结构的晶胞在压力作用下呈现出了压缩率各项异性的特点。通过三阶BM方程拟合，我们得到常压相的体弹模量为B0=24.5±3.5GPa，B0’=3.4±3.2。当压力增加到2.9GPa时发生了一次结构相变。压制结构相变过程中晶胞参数a和c趋近相同。所以，我们推断，这一相变为一个可逆的从正交结构→四方结构的二级结构相变。相变后所有振动模式在高压相中保持原有的指认，表明叠氮化铵在高压相中始终以叠氮根离子和铵根离子的形式存在，并且它们仍然以氢键相连接，从N H对称伸缩振动模式频率的变化以及波数位于420cm-1处铵根离子的扭曲振动模式相对强度的变化，我们可以确定氢键的键能在0~2.9GPa范围内减弱、在2.9~12GPa范围内增强并且在12~20GPa范围内再次发生减弱。在2.9GPa处的变化是由结构相变所引起的，而在12GPa处的变化是由叠氮根离子的旋转或弯折作用所引起的，并不伴随结构相变的发生。 2.在室温条件下对叠氮化钙（Ca(N3)2）进行了原位高压X射线衍射光谱、原位高压拉曼光谱以及原位高压远红外和中红外吸收光谱的研究。实验所达到的最高压力分别为54GPa、19.2GPa、23GPa以及31GPa。整个实验压力范围内，没有发现结构相变。实验中得到的叠氮化钙的零压体模量以及体模量的压力导数分别为B0=41.22±1.14GPa，B0′=5.3±0.04，这一数值高于所有碱金属叠氮化物，这是由于金属与叠氮根之间的键合的离子性不同所导致的。为了分析和指认所有实验中观测到的振动模式，我们利用CESTEP模块对常压下叠氮化钙的拉曼光谱和红外光谱进行了理论计算。在振动光谱的高压研究中，我们观察到某些外模振动以及叠氮根的内模弯曲振动模式（ν2）在0~7GPa范围内发生软化，在~7GPa以后又发生硬化。这一现象与高压同步辐射XRD衍射中得到的FE fE曲线在7.1GPa处发生拐点的现象一致。这很有可能是由叠氮根之间发生的压缩作用以及叠氮根本身的旋转和弯折作用，交替成为叠氮根在压力作用下的主导行为所引起的。由于原子间距离和键能的变化会引起电子云的转移，所以这些变化可能是由于叠氮化钙发生了电子相变引起的。 3.我们对叠氮化锶（Sr(N3)2）进行了高压X-ray同步辐射实验，实验所达到的最高压力为33.5GPa。整个实验压力范围内，没有发现结构相变。实验中得到的叠氮化锶的零压体模量以及体模量的压力导数分别为B0=55.00±0.56GPa，B0′=4，，这一数值值高于所有已报道过的金属叠氮化物，这是由于金属与叠氮根之间的键合的离子性不同所导致的。 4.室温下进行的叠氮化钡（Ba(N3)2）高压同步辐射X-ray衍射研究实验所达到的最高压力为28GPa。常压相结构的晶胞参数a、b、c在压力的作用下以不同的速度被压缩，压缩率分别为99.47%、99.27%以及99.95%，呈现出了各项异性的特点，压缩程度由大到小的顺序为b a c。其中，b轴是最容易被压缩的，这是由于叠氮化钡晶体为层状结构，所有的钡离子和叠氮根离子都位于平行于(010)平面的一个平面内，层与层之间较容易被压缩。a轴的压缩性最小，这是因为相邻的叠氮根（I）之间距离最短，排斥力也就最强。叠氮根离子间的排斥力作用以及(100)和(001)平面的滑移作用主导了叠氮化钡的压缩性质。当压力增加到2.6GPa以后，高压同步辐射X-ray衍射图谱中发生了一些变化，出现了一些新峰，表明开始发生了一次结构相变。我们将它定义为一次等结构相变，同I相一样，II相仍为单斜结构，空间群仍为P21/m。当压力继续增加到11.8GPa，同步辐射衍射图谱中又出现了一些新的衍射峰，表明又发生了一次结构相变，此新相的结构保持到了28.0GPa。并且压力下这一系列结构的变化是可逆的。
[Abstract]:in that pap, high-pressure experimental technology such as in-situ high-voltage synchronous radiation X-ray diffraction, in-situ high-pressure Raman scattering spectrum and in-situ high-pressure infrared absorption spectrum are adopted, The phase transition of the high-voltage structure and the structural stability of the azido-and alkaline-earth metal azide are studied. A series of high-pressure new phases were found through a series of high-pressure experiments. The phase transition in high pressure of alkaline-earth metal azide is summarized. 1. In normal temperature, the in-situ high-voltage synchrotron radiation X-ray diffraction, in-situ high-pressure Raman spectrum and in-situ high-pressure infrared absorption spectrum were carried out for the in-situ high-pressure synchrotron radiation. The highest pressures reached in the experiment were 50.5 GPa, 22.4 GPa and 20 GP, respectively. A. Because of the orientation of the azido ion, the unit cell of the orthogonal structure exhibits the opposite of the compression rate under the action of pressure. Point. By fitting the third-order BM equation, the bulk elastic modulus of the normal pressure phase is B0 = 24.5-3.5 GPa, and B0 '= 3.4-3. 2. A structural phase occurs when the pressure is increased to 2.9 GPa the crystal cell parameters a and c approach phase in the process of phase change of the pressing structure In the same way, we conclude that this phase becomes a reversible secondary structural phase from an orthogonal structure to a tetragonal structure. All vibration modes after phase change maintain the original designation in the high pressure phase, indicating that the azido is always present in the form of an azido ion and a radical ion in the high-pressure phase, and they are still connected in hydrogen bonds It can be determined that the bond energy of the hydrogen bond can be reduced in the range of 0 to 2.9 GPa and the decrease of the wave number at 420 cm-1 at 420 cm-1, which is increased in the range of 2.9 to 12 GPa and is reduced again in the range of 12 to 20 GPa. Weak. The change at 2.9 GPa is caused by the phase transition of the structure, while the change at 12 GPa is caused by the rotation or bending of the azide ions and does not accompany the formation of the structural phase change 2. In-situ high-pressure X-ray diffraction, in-situ high-pressure Raman spectroscopy and in-situ high-pressure far-infrared and mid-infrared absorption spectra for calcium azide (Ca (N3)2) at room temperature The highest pressures reached in the experiment were 54 GPa, 19.2 GPa,23 GPa and 31, respectively. GPa. No knots were found throughout the experimental pressure range. The zero-pressure body modulus of the azido-calcium obtained in the experiment and the pressure derivative of the bulk modulus are B0 = 41.22-1.14 GPa, and the B0-type = 5.3-0.04, which is higher than all the alkali metal azide, which is due to the different ionic nature of the bonding between the metal and the azido. In order to analyze and identify the vibration modes observed in all the experiments, the Raman spectrum and the infrared spectrum of the azido calcium under normal pressure were studied by means of the CESTEP module. In the high-pressure study of the vibration spectrum, we observed that some of the outer-mold vibration and the inner-mold bending vibration mode of the azido-radical were softened in the range of 0-7 GPa, and after ~ 7 GPa The phenomenon that the FE-E curve obtained in the XRD diffraction of high-pressure synchrotron radiation has an inflection point at 7.1 GPa. This is likely to be the compression action that occurs between the azido and the rotation and bending of the azido body, alternating into the dominant behavior of the azido under pressure. It is caused by the change of the interatomic distance and the key energy, which can lead to the transfer of the electron cloud, so that these changes may be due to the electronic phase change of the azido calcium. Induced.3. We conducted a high-pressure X-ray synchrotron radiation experiment on the azido (Sr (N3)2). The maximum pressure reached by the experiment was 33. .5 GPa. In the entire experimental pressure range, no hair is produced. The zero-pressure body modulus and the pressure derivative of the bulk modulus obtained in the experiment are B0 = 55.00, 0.56 GPa, and B0 = 4, and this value is higher than all reported metal azide, since the ionic nature of the bonding between the metal and the azido is not The highest pressure reached by the high-pressure synchrotron radiation X-ray diffraction study in the high-pressure synchrotron radiation of Ba (N3)2) carried out at room temperature And the compression ratio is 99.47%, 99.27% and 99.95%, respectively. It is most easily compressed, since the azido crystal is a layered structure, all of the ionization ions and the azido ions are in a plane parallel to the (010) plane, and the layer and the layer the compressibility of the a-axis is minimal because the distance between adjacent azido (i) is the shortest, The repulsive force is also the strongest. The repulsive force between the azide ions and the sliding action of the (100) and (001) planes dominate the azido. When the pressure is increased to 2.6 GPa, some changes have taken place in the X-ray diffraction pattern of the high-pressure synchronous radiation, and some new peaks appear, indicating the beginning of the occurrence We define it as an isostructural phase change, which is the same as the I phase, and the phase II is still a monoclinic structure, and the space group It is still P21/ m. When the pressure is increased to 11.8 GPa, some new diffraction peaks appear in the synchrotron radiation diffraction pattern. 28.0 gpa. and the series of structures under pressure
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ126.2

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