铁酸铋陶瓷光学特性的理论计算研究

发布时间：2018-04-20 21:25

本文选题：密度泛函理论 + BiFeO3　；参考：《青岛大学》2015年硕士论文

【摘要】：BiFeO3是多铁材料的一种,具有铁电性、铁磁性和反铁磁性,在传感器、铁电存贮器等方面有很好的潜在应用价值,近年来BiFeO3在光伏领域又有了新的研究进展,因此其光电特性成为了研究热点。本论文采用第一性原理方法计算研究了多铁材料中BiFeO3在纯相和掺杂两种情况下的几何结构,电子特性,光学性质。重点讨论了单相BiFeO3陶瓷的光吸收以及稀土元素掺杂对其吸收光谱的影响。我们首先运用了第一性原理密度泛函理论中的局域自旋密度近似加U(LSDA+U)方法对单相BiFeO3的带隙进行了调节,计算结果显示,当U值等于16.5ev时,BFO的带隙值为2.418ev且为间接带隙,这与实验测试值2.5ev左右相符。在此基础上我们分别计算了其电子结构及光学性质。结果发现,紫外区域的吸收效果非常好,在可见光范围内当入射光波长在400nm左右时吸收效果最好,根据可见光光谱范围其对应的入射光是紫光,对应着从O 2p(向上)态到Fe 3d(向下)态的电子跃迁。第四章是有关稀土元素Co对铁电体BiFeO3斜六方相B位掺杂对其态密度以及光学吸收影响的研究。结果发现,掺杂以后吸收光谱的范围从可见光变到了紫外区域。这可以从侧面说明Co元素B位掺杂BiFeO3对其光吸收光谱的影响是发生蓝移。
[Abstract]:BiFeO3 is a kind of multi-iron material, which has ferroelectricity, ferromagnetism and antiferromagnetism. It has good potential application value in sensor, ferroelectric memory and so on. In recent years, BiFeO3 has made new progress in photovoltaic field. Therefore, its photoelectric characteristics have become a research hotspot. In this paper, the geometrical structure, electronic properties and optical properties of BiFeO3 in pure phase and doped multiferric materials have been calculated and studied by first-principle method. The light absorption of single phase BiFeO3 ceramics and the effect of rare earth element doping on their absorption spectra were discussed. We first use the local spin density approximation plus U(LSDA U) method in the first principle density functional theory to adjust the band gap of the single-phase BiFeO3. The calculated results show that the band gap of the single phase BiFeO3 is 2.418ev and indirect band gap when the U value is equal to 16.5ev. This is consistent with the experimental value of 2.5ev. On this basis, the electronic structure and optical properties are calculated respectively. The results show that the absorption effect in the ultraviolet region is very good, and the absorption effect is the best when the incident wavelength is about 400nm in the visible range. According to the visible spectrum range, the incident light is purple. It corresponds to the electron transition from O 2p (upward) state to Fe 3d (downward) state. In chapter 4, the effects of rare earth Co doping on the density of states and optical absorption of ferroelectric BiFeO3 obliquely hexagonal B site are studied. The results show that the range of absorption spectrum changes from visible light to ultraviolet region after doping. It can be seen from the side that the effect of BiFeO3 doping on the optical absorption spectrum is blue shift.
【学位授予单位】：青岛大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.1

【参考文献】