稀土元素掺杂二氧化钛光学材料的结构和光学特性研究
发布时间：2019-02-26 15:13
【摘要】：宽禁带半导体光学材料二氧化钛(Ti O2)以其优良的光电性能、高光能转换效率、强氧化性、无毒等特性,在太阳能电池及光催化等技术领域具有重要的应用,使其成为当前的研究热点。然而,由于Ti O2材料本身的属性,许多潜在的应用受到严重的限制,其中禁带宽度较大(~3.2 e V)与锐钛矿相位的亚稳定性是影响其应用的主要因素。利用金属及非金属离子掺杂改性是拓展二氧化钛应用的重要手段之一。稀土元素的丰富能级结构使其具有优异的光、电、磁和催化性能,从而在半导体材料领域得到重要关注。近年,稀土元素(La,Ce,Pr,Eu,Dy等)掺杂Ti O2在光催化、太阳能电池及气敏传感器等领域获得了大量的理论及实验研究,结果表明稀土元素掺杂可以有效改善Ti O2的光催化特性以及提高锐钛矿相的稳定性。本论文研究了稀土元素铥(Tm)及钕(Nd)掺杂对锐钛矿相及金红石相Ti O2的结构和性能的影响。该研究基于密度泛函理论的CASTEP模块,采用GGA-PBE泛函构造了不同掺杂浓度模型,通过量子力学第一性原理计算分析了稀土元素Tm及Nd分别掺杂Ti O2体系的能带结构、电子态密度及光学性质。其主要研究结果有:(1)利用稀土元素Tm替位掺杂锐钛矿相及金红石相Ti O2中的Ti原子,构建了三种不同掺杂浓度(1.39 at%,2.08 at%及4.17 at%)的物理模型,计算分析了掺杂体系的电子结构及光学吸收特性等。能带结构及电子态密度研究结果表明,由于稀土元素Tm的引入,在Ti O2禁带中形成了Tm-4f杂质能级,从而有效地减小了其带隙宽度。其中,锐钛矿相在1.39 at%的掺杂浓度下带隙宽度减小约0.24 e V,金红石相在4.17 at%的掺杂浓度下带隙宽度减小约0.13 e V。光学特性分析结果表明,稀土Tm掺杂锐钛矿相Ti O2体系的光学吸收谱具有明显红移特性。(2)利用稀土元素Nd替位掺杂锐钛矿相及金红石相Ti O2中的Ti原子,构建了三种不同掺杂浓度(1.39 at%,2.08 at%及4.17 at%)的物理模型,计算分析了掺杂体系的电子结构及光学吸收特性等。能带结构及电子态密度研究结果表明,由于稀土元素Nd的引入,在Ti O2禁带中形成了Nd-4f杂质能级,从而有效地减小了其带隙宽度。其中,锐钛矿相在4.17at%的掺杂浓度下带隙宽度减小约0.91 e V,金红石相在4.17at%的掺杂浓度下带隙宽度减小约1.06 e V。光学特性分析结果表明,稀土Nd掺杂金红石相Ti O2体系的光学吸收谱无明显变化。
[Abstract]:Titanium dioxide (Ti O2), a wide band gap semiconductor optical material, has been widely used in solar cells and photocatalysis due to its excellent optical and electrical properties, high photoenergy conversion efficiency, strong oxidation and non-toxicity. Make it become the current research hotspot. However, due to the properties of Ti O2 material itself, many potential applications are seriously limited, among which the wide band gap (~ 3.2 e V) and anatase phase metastability is the main factor affecting its application). Doping modification with metal and non-metallic ions is one of the important means to expand the application of titanium dioxide. The rich energy-level structure of rare earth elements makes it have excellent optical, electrical, magnetic and catalytic properties, so it has attracted great attention in the field of semiconductor materials. In recent years, rare earth elements (La,Ce,Pr,Eu,Dy, et al.) doped Ti O2 have been studied theoretically and experimentally in the fields of photocatalysis, solar cells and gas sensors. The results show that rare earth doping can effectively improve the photocatalytic properties of Ti O 2 and improve the stability of anatase phase. The effects of thulium (Tm) and neodymium (Nd) doping on the structure and properties of anatase and rutile Ti O 2 were studied in this paper. Based on the CASTEP module of density functional theory, the different doping concentration models were constructed by using GGA-PBE functional. The energy band structures of rare earth elements Tm and Nd doped Ti O2 system were analyzed by quantum mechanics first principle calculation. Electronic density of states and optical properties. The main results are as follows: (1) the physical models of three different doping concentrations (1.39 at%,2.08 at% and 4.17 at%) were constructed by using the anatase phase doped with rare earth element Tm and the Ti atom in rutile phase Ti O 2. The electronic structure and optical absorption characteristics of the doped system were calculated and analyzed. The results of energy band structure and electron density of states show that due to the introduction of rare earth element Tm, Tm-4f impurity energy levels are formed in the band gap of Ti O 2, thus the band gap width is reduced effectively. Among them, the band gap width of anatase phase decreases about 0.24 EV at the doping concentration of 1.39 at%, and the band gap width of rutile phase decreases about 0.13 EV at the doping concentration of 4.17 at%. The results of optical properties analysis show that the optical absorption spectra of the anatase phase Ti O 2 doped by rare earth Tm have obvious red shift. (2) the Ti atoms in the anatase phase and rutile phase Ti O 2 are doped by the substitution of rare earth element Nd. The physical models of three different doping concentrations (1.39 at%,2.08 at% and 4.17 at%) were constructed. The electronic structure and optical absorption characteristics of the doping system were calculated and analyzed. The results of energy band structure and electron density of states show that due to the introduction of rare earth element Nd, Nd-4f impurity energy levels are formed in the band gap of Ti O 2, thus the band gap width is reduced effectively. Among them, the band gap width of anatase phase decreases about 0.91 EV at 4.17 at% doping concentration, and the band gap width of rutile phase decreases about 1.06 EV at 4.17 at% doping concentration. The results of optical properties analysis show that the optical absorption spectra of rutile phase Ti O 2 doped with rare earth Nd have no obvious change.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.2
本文编号：2430899
[Abstract]:Titanium dioxide (Ti O2), a wide band gap semiconductor optical material, has been widely used in solar cells and photocatalysis due to its excellent optical and electrical properties, high photoenergy conversion efficiency, strong oxidation and non-toxicity. Make it become the current research hotspot. However, due to the properties of Ti O2 material itself, many potential applications are seriously limited, among which the wide band gap (~ 3.2 e V) and anatase phase metastability is the main factor affecting its application). Doping modification with metal and non-metallic ions is one of the important means to expand the application of titanium dioxide. The rich energy-level structure of rare earth elements makes it have excellent optical, electrical, magnetic and catalytic properties, so it has attracted great attention in the field of semiconductor materials. In recent years, rare earth elements (La,Ce,Pr,Eu,Dy, et al.) doped Ti O2 have been studied theoretically and experimentally in the fields of photocatalysis, solar cells and gas sensors. The results show that rare earth doping can effectively improve the photocatalytic properties of Ti O 2 and improve the stability of anatase phase. The effects of thulium (Tm) and neodymium (Nd) doping on the structure and properties of anatase and rutile Ti O 2 were studied in this paper. Based on the CASTEP module of density functional theory, the different doping concentration models were constructed by using GGA-PBE functional. The energy band structures of rare earth elements Tm and Nd doped Ti O2 system were analyzed by quantum mechanics first principle calculation. Electronic density of states and optical properties. The main results are as follows: (1) the physical models of three different doping concentrations (1.39 at%,2.08 at% and 4.17 at%) were constructed by using the anatase phase doped with rare earth element Tm and the Ti atom in rutile phase Ti O 2. The electronic structure and optical absorption characteristics of the doped system were calculated and analyzed. The results of energy band structure and electron density of states show that due to the introduction of rare earth element Tm, Tm-4f impurity energy levels are formed in the band gap of Ti O 2, thus the band gap width is reduced effectively. Among them, the band gap width of anatase phase decreases about 0.24 EV at the doping concentration of 1.39 at%, and the band gap width of rutile phase decreases about 0.13 EV at the doping concentration of 4.17 at%. The results of optical properties analysis show that the optical absorption spectra of the anatase phase Ti O 2 doped by rare earth Tm have obvious red shift. (2) the Ti atoms in the anatase phase and rutile phase Ti O 2 are doped by the substitution of rare earth element Nd. The physical models of three different doping concentrations (1.39 at%,2.08 at% and 4.17 at%) were constructed. The electronic structure and optical absorption characteristics of the doping system were calculated and analyzed. The results of energy band structure and electron density of states show that due to the introduction of rare earth element Nd, Nd-4f impurity energy levels are formed in the band gap of Ti O 2, thus the band gap width is reduced effectively. Among them, the band gap width of anatase phase decreases about 0.91 EV at 4.17 at% doping concentration, and the band gap width of rutile phase decreases about 1.06 EV at 4.17 at% doping concentration. The results of optical properties analysis show that the optical absorption spectra of rutile phase Ti O 2 doped with rare earth Nd have no obvious change.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.2
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