稀土元素摻雜二氧化鈦光學(xué)材料的結(jié)構(gòu)和光學(xué)特性研究
發(fā)布時間：2019-02-26 15:13
【摘要】：寬禁帶半導(dǎo)體光學(xué)材料二氧化鈦(Ti O2)以其優(yōu)良的光電性能、高光能轉(zhuǎn)換效率、強氧化性、無毒等特性,在太陽能電池及光催化等技術(shù)領(lǐng)域具有重要的應(yīng)用,使其成為當前的研究熱點。然而,由于Ti O2材料本身的屬性,許多潛在的應(yīng)用受到嚴重的限制,其中禁帶寬度較大(~3.2 e V)與銳鈦礦相位的亞穩(wěn)定性是影響其應(yīng)用的主要因素。利用金屬及非金屬離子摻雜改性是拓展二氧化鈦應(yīng)用的重要手段之一。稀土元素的豐富能級結(jié)構(gòu)使其具有優(yōu)異的光、電、磁和催化性能,從而在半導(dǎo)體材料領(lǐng)域得到重要關(guān)注。近年,稀土元素(La,Ce,Pr,Eu,Dy等)摻雜Ti O2在光催化、太陽能電池及氣敏傳感器等領(lǐng)域獲得了大量的理論及實驗研究,結(jié)果表明稀土元素摻雜可以有效改善Ti O2的光催化特性以及提高銳鈦礦相的穩(wěn)定性。本論文研究了稀土元素銩(Tm)及釹(Nd)摻雜對銳鈦礦相及金紅石相Ti O2的結(jié)構(gòu)和性能的影響。該研究基于密度泛函理論的CASTEP模塊,采用GGA-PBE泛函構(gòu)造了不同摻雜濃度模型,通過量子力學(xué)第一性原理計算分析了稀土元素Tm及Nd分別摻雜Ti O2體系的能帶結(jié)構(gòu)、電子態(tài)密度及光學(xué)性質(zhì)。其主要研究結(jié)果有:(1)利用稀土元素Tm替位摻雜銳鈦礦相及金紅石相Ti O2中的Ti原子,構(gòu)建了三種不同摻雜濃度(1.39 at%,2.08 at%及4.17 at%)的物理模型,計算分析了摻雜體系的電子結(jié)構(gòu)及光學(xué)吸收特性等。能帶結(jié)構(gòu)及電子態(tài)密度研究結(jié)果表明,由于稀土元素Tm的引入,在Ti O2禁帶中形成了Tm-4f雜質(zhì)能級,從而有效地減小了其帶隙寬度。其中,銳鈦礦相在1.39 at%的摻雜濃度下帶隙寬度減小約0.24 e V,金紅石相在4.17 at%的摻雜濃度下帶隙寬度減小約0.13 e V。光學(xué)特性分析結(jié)果表明,稀土Tm摻雜銳鈦礦相Ti O2體系的光學(xué)吸收譜具有明顯紅移特性。(2)利用稀土元素Nd替位摻雜銳鈦礦相及金紅石相Ti O2中的Ti原子,構(gòu)建了三種不同摻雜濃度(1.39 at%,2.08 at%及4.17 at%)的物理模型,計算分析了摻雜體系的電子結(jié)構(gòu)及光學(xué)吸收特性等。能帶結(jié)構(gòu)及電子態(tài)密度研究結(jié)果表明,由于稀土元素Nd的引入,在Ti O2禁帶中形成了Nd-4f雜質(zhì)能級,從而有效地減小了其帶隙寬度。其中,銳鈦礦相在4.17at%的摻雜濃度下帶隙寬度減小約0.91 e V,金紅石相在4.17at%的摻雜濃度下帶隙寬度減小約1.06 e V。光學(xué)特性分析結(jié)果表明,稀土Nd摻雜金紅石相Ti O2體系的光學(xué)吸收譜無明顯變化。
[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.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN304.2
本文編號：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.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN304.2
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