【作者】 朱振华；

【导师】 雷明凯；

【作者基本信息】 大连理工大学 ， 材料表面工程， 2008， 博士

【摘要】 采用非水性sol-gel法，通过Er³⁺和Er³⁺-Yb³⁺共掺杂，获得具有中心波长为1．533μm光致发光（PL）特性的稀土掺杂Al₂O₃。系统研究了SiO₂和P₂O₅复合对掺Er³⁺：Al₂O₃结构和近红外光致发光特性的影响规律，讨论了氧化物复合对光致发光的增强作用。通过干燥控制化学添加剂（DCCA，Drying Control Chemical Addtive）和干燥控制物理添加剂（DCPA，Drying Control Physical Addtive）改性溶胶，控制薄膜的干燥，解决了凝胶化过程中的开裂现象，并显著增加了薄膜工艺的沉积效率，讨论了改善薄膜工艺质量的机理。以异丙醇铝[Al（OC₃H₇）₃]为前驱体，稀土硝酸盐Er（NO₃）₃·5H₂O为掺杂介质，在异丙醇（PrⁱOH）的非水性环境下水解合成稀土掺杂Al₂O₃溶胶，在550-1200℃烧结制备掺Er³⁺：Al₂O₃粉末。建立了掺0-5．0 mol％Er³⁺：Al₂O₃构成的Er-Al-O系相组成图。体系中存在γ-（Al,Er）₂O₃，θ-（Al,Er）₂O₃，α-（Al,Er）₂O₃，ErAlO₃（ErAP）和Er₃Al₅O₁₂（ErAG）等5种相。随掺Er³⁺浓度的提高，γ和θ相Al₂O₃非晶化加剧，且对Al₂O₃的γ→θ→α相变抑制作用增强。Er³⁺掺杂Al₂O₃粉末以γ，θ相为主时，获得了近红外区1．533μm处主峰和1．556μm处肩峰双峰结构的PL谱。Al₂O₃转变至稳定的α相，ErAG与ErAP化合物析出，则PL谱由宽峰劈裂为多峰结构。θ与γ-Al₂O₃存在一定比例无序分布的阳离子空位，结晶程度较低。晶体场环境的多样性导致Er³⁺的第一激发态⁴I_13／2向基态⁴I_15／2跃迁，形成以1．533μm为中心波长，非均匀加宽的宽峰PL谱。α相中同样存在阳离子空位，Er³⁺确定的晶体场环境导致非均匀加宽效应显著弱化，形成多峰PL谱。掺0．002-2．5 mol％Er³⁺：α-Al₂O₃粉末的低温PL谱表明，0．01 mol％Er³⁺低于α相的溶解度上限，固溶的Er³⁺对掺Er³⁺：α-Al₂O₃近红外区发光贡献显著。在高掺杂Er³⁺浓度时，化合物ErAG对近红外区发光同样具有贡献。但化合物ErAG与ErAP更有利于Er³⁺由较高激发态向基态的的跃迁，易在可见光区发射，而α-Al₂O₃晶格中Er²⁺的发光则更有利于较低激发态向基态的跃迁，在近红外区更易被观察到。以正硅酸乙酯（TEOS）为前驱体，制备稀土掺杂SiO₂溶胶，通过与Al₂O₃溶胶混合制备了掺Er³⁺：SiO₂-Al₂O₃复合体系氧化物。掺Er³⁺：SiO₂-Al₂O₃粉末在1200℃烧结，仍以γ，θ相Al₂O₃结构为主，同时有α-Al₂O₃与Al₆Si₂O₁₃相形成。Al₂O₃基体中复合SiO₂抑制了γ→θ→α相的转变，大量Er³⁺仍位于γ，θ-Al₂O₃晶格中，PL谱保持中心波长1．533μm的宽峰结构。PL强度和1．533μm荧光寿命，随烧结温度提高及SiO₂复合量的增加均显著增加。SiO₂复合为Er³⁺提供了多样的晶体场环境，使ErO₆八面体的对称度低于单一Al₂O₃体系，更有利于Er³⁺的激发态⁴I_13／2向基态⁴I_15/2能级的跃迁。通过在溶胶中加入磷酸三乙酯（TEP，（CH₃CH₂O）₃P=O）形成掺1．0 mol％Er³⁺：P₂O₅-Al₂O₃复合体系氧化物，促进了掺Er³⁺：Al₂O₃中残余-OH的脱除。P₂O₅复合量增至30 mol％，1000℃烧结，可以实现FT-IR光谱3300-3600 cm^-1波段的-OH振动吸收消逝。P₂O₅复合在基体中引入了振动能量在1300-1600 cm^-1之间的P-O键，其振动对Er³⁺的⁴I_13／2能级辐射依赖的⁴I_11/2能级向⁴I_13／2能级无辐射过程有更为显著的增强作用。P₂O₅复合量增加，既降低了-OH含量，又提高了泵浦效率，双重的作用增强了Er³⁺的光致发光。利用J-O理论计算掺1．0 mol％Er³⁺：P₂O₅-Al₂O₃复合体系氧化物的强度因子Ω_λ（λ=2，4，6），并拟合得到了Er³⁺各能级光谱参数。结果显示随P₂O₅复合量的提高，Ω_2,4,6都呈现减小的趋势，表明P₂O₅的复合提高了基体的离子性。计算得到的第一激发态⁴I_13／2的能级寿命随P₂O₅复合量的增加而略有增加，与实验得到的P₂O₅复合量对测量荧光寿命的影响规律一致。以N,N-二甲基甲酰胺（DMF）作为DCCA，以乙醇、丙醇作为DCPA，分别对稀土掺杂Al₂O₃溶胶改性，通过浸渍提拉工艺在SiO₂／Si（100）基体上沉积稀土离子掺杂的Al₂O₃薄膜，抑制薄膜在干燥过程中的开裂现象。高浓度1．0 mol％Er³⁺-10．0 mol％Yb³⁺共掺Al₂O₃溶胶，经过40次循环提拉，1000℃烧结，可分别得到表面均匀、光滑、无开裂、厚度约为1．5μm和0．8μm，适合光学应用的稀土掺杂Al₂O₃薄膜。以聚乙烯吡咯烷酮（PVP）为增粘剂，调节DCPA改性的溶胶粘度，随着PVP聚合度及加入量的增大，溶胶粘度显著提高，当PVP（K90）与Al（OC₃H₇）₃的摩尔比为1：1时，溶胶粘度由原始的2．3mPa·s增大到31．5 mPa·s，形成的单层氧化物膜厚由20 nm提高至160 nm，在干燥和烧结过程中薄膜不出现开裂，将sol-gel法薄膜工艺沉积效率提高了近一个数量级。在1．400-1．700μm波段获得了以1．533μm为中心的宽峰PL谱。采用DCCA，DCPA和增粘剂改性溶胶对稀土掺杂氧化物薄膜的PL特性无影响。更多还原

【Abstract】 The Er³⁺-doped and Er³⁺-Yb³⁺ codoped Al₂O₃ with the photoluminescence （PL） properties in the near infrared region centered at 1.53μm were prepared by using a non-aqueous sol-gel method. The effects of mixing of SiO₂/P₂O₅ on phase structure and PL properties of the Er³⁺-doped Al₂O₃ were systematically investigated to explore the enhancement mechanism of PL properties of Er³⁺-doped Al₂O₃ due to the mixing of oxides. The cracking in the thin films has been suppressed by introducing drying control chemical additive （DCCA） and drying control physical additive （DCPA） in the sols, respectively. The deposition efficiency of the sol-gel dip-coating has been improved by introducing the viscosity increaser （VI）. The mechanisms of suppressed cracking and increase of the deposition efficiency for the rare earth ions doped Al₂O₃ thin films in sol-gel method have been discussed.The Er³⁺-doped Al₂O₃ powders sintered at different temperatures were prepared by using the aluminum isopropoxide [Al（OC₃H₇）₃] as precursor, acetylacetone （AcAcH） as chelating agent, nitric acid （HNO₃） as catalyzer, and hydrated nitrate of Er（NO₃）₃·5H₂O as dopant in the non-aqueous isopropanol environment. The phase contents diagram for the Er-Al-O system with the doping concentration up to 5.0 mol% was described at the sintering temperature from 550℃to 1250℃. There were three crystalline types of Er³⁺-doped Al₂O₃ phases,γ,θandα-（Al,Er）₂O₃, and two stoichiometric compounds composed of Al, Er, and O, the perovskite ErAlO₃ （ErAP） and garnet Er₃Al₅O₁₂ （ErAG）, in the Er-Al-O phase contents diagram. The Er³⁺ doping suppressed the crystallization of theγandθphases and delayed the phase transitions ofγ→θandθ→α.The PL spectra in the wavelength range from 1.400μm to 1.700μm with a main peak at 1.535μm and a side peak at 1.556μm were obtained for the Er³⁺-doped Al₂O₃ with theγphase and the mixture ofγandθphases. The PL spectra were splitting with the appearance ofα-Al₂O₃, ErAP and ErAG phases in the matrix, due to a definite local environment in theα-（Al,Er）₂O₃, ErAP and ErAG lattices, and a weaker effect of inhomogeneous widening than in theγandθ-Al₂O₃ phase. The low temperature PL spectra of Er³⁺-dopedα-Al₂O₃ powders in the doping concentration range from 0.002 to 2.5 mol% indicated that a very low concentration of Er³⁺ could resolute inα-Al₂O₃ lattice. The combining photoluminescence of Er³⁺-dopedα-Al₂O₃ unambiguously was mainly derived from the Er³⁺ which replaced with Al³⁺ inα-Al₂O₃ lattice （α-（Al,Er）₂O₃）. For the Er³⁺ concentration of 0.5 -5.0 mol%, the luminescence was from two different kinds of optical centers, the ErAG andα-（Al,Er）₂O₃, respectively, and the former mainly benefits to the visible emission, while the latter prefers to contribute to the near-infrared luminescence.The Er³⁺-doped SiO₂-Al₂O₃ powders were prepared by mixing of SiO₂ sol and Al₂O₃ sol with same doping concentration. The phase transitions ofγ→θandθ→αof the 0.1 mol %Er³⁺-doped Al₂O₃ were suppressed by mixing of SiO₂, and the 0.1 mol %Er³⁺-doped Al₂O₃ was mainly of theγandθ-Al₂O₃ phases with a mount ofα-Al₂O₃ and Al₆Si₂O₁₃ phase for the sintering temperature below 1200℃. The PL spectra maintained a single broadband centered at 1.53μm even though the sintering temperature was up to 1200℃. The PL lifetime and intensity at the wavelength of 1.53μm increased obviously with the increase of the sintering temperature and mixing content of SiO₂, due to the decrease in -OH content and the formation of lower symmetrical octahedral ErO₆, respectively.The 1.0 mol% Er³⁺-doped P₂O₅-Al₂O₃ powders sintered at the temperatures of 1000℃were prepared by introduced triethyl phosphate （TEP, （CH₃CH₂O）₃P=O） in the sols. The -OH has been removed completely due to the addition of TEP with an increased molar ratio to 30.0 mol%. The vibrate energy of P-O bond is about 1300-1600 cm^-1, which contribute to the transition of the second excited state ⁴I_11/2 to the first excited state ⁴I_13/2. Both the removing of the -OH and the introducing of the P-0 bond led to the increasing of PL properties. The J-0 parametersΩ_λ（λ=2, 4, 6） and radiative transition probabilities of the Er³⁺-doped P2O5-Al₂O₃ powders were calculated by the J-O theory. The J-O parametersΩ_2,4,6 were all reduced with the mixing content of P₂O₅ increased, indicating that the ionicity of the materials was enhanced. The radiation lifetime of ⁴I_13/2 was increased gently with increasing the mixing content of P₂O₅, which coincided with the variety of measured lifetime.The cracking in the thin films was suppressed by introducing drying control chemical additive （DCCA） and drying control physical additive （DCPA） in the sols to modify the Al₂O₃ sols, respectively. The homogeneous, uniform and crack-free 1.0 mol%Er³⁺-10.0 mol%Yb³⁺ codoped Al₂O₃ thin films on the thermally oxidized SiO2/Si（100） substrate were formed by 40 dip-coating cycles. Polyringlpyrrolidone （PVP） as a viscosity increaser was used to adjust the viscosity of the sols. When the molar ratio of PVP（K90）:AlOC₃H₇ was up to 1:1, the viscosity of the PVP assisted sol increased from 2.3 to 31.5 mPa·s, and homogeneous, uniform and crack-free 1.0 mol%Er³⁺-10.0 mol%Yb³⁺ codoped Al₂O₃ thin films with the thickness of 1.6μm were formed by 10 dipping and drying cycles sintered at 1000℃. The deposition efficiency of the crack-free thin films by the sol-gel method was increased by about one order in magnitude. The PL spectra of Er³⁺-Yb³⁺ codoped Al₂O₃ thin films in the wavelength range from 1.400μm to 1.700μm centered at 1.535μm were measured by the face coupling method. The drying control additive and viscosity increaser have no effect on the strong PL of the Er³⁺-Yb³⁺ codoped Al₂O₃ thin films.更多还原