【作者】 张海萍；

【导师】 吕孟凯；

【作者基本信息】 山东大学 ， 材料学， 2007， 博士

【摘要】 论文分为两部分。第一部分是钒酸盐纳米材料的制备、表征及发光性能研究，这是我们研究的主要内容；第二部分是钛酸铋系薄膜的制备、表征及光催化性能研究。发光材料是重要的功能材料之一，在照明、显示、荧光探测、光电器件等领域有着广泛的应用。随着纳米技术的迅速发展，纳米发光材料由于显示出许多体块材料所不可比拟的新的光学特性而成为人们关注和研究的热点。钒酸盐具有良好的化学稳定性和热稳定性，但对其荧光性能的研究相对较少，在本论文中，我们采用不同的合成方法制备了钒酸盐纳米发光材料，并系统地研究了其发光性质，以寻求具有高性能的新型发光材料。在第一章中，我们简单阐述了固体发光理论，对纳米材料的基本性质、纳米发光材料的制备方法、纳米发光材料的特性进行了简要介绍，并对钒酸盐发光材料的研究概况进行了总结。随着新型平板显示器的发展，要求具有更高发光效率、更纯发光颜色的发光材料，以稀土钒酸盐为基质的发光材料性能优良，因而引起人们较大的研究兴趣。在第二章中，我们采用沉淀法、燃烧法制备了以稀土钒酸盐（YVO₄、LaVO₄）为基质的纳米发光材料，并研究了其发光性质。①首次采用柠檬酸为燃料／还原剂、硝酸盐为氧化剂的溶胶-凝胶燃烧法成功制备了不同尺寸的YVO₄：Eu³⁺纳米晶，并系统研究了制备参数，如退火温度、柠檬酸／硝酸盐的摩尔比及硝酸锂添加剂的量，对YVO₄：5mol％Eu³⁺纳米颗粒发光性质的影响。研究表明，YVO₄：Eu³⁺纳米晶的发光强度随退火温度的升高而升高，这表明在纳米尺寸范围内高的退火温度对发光强度是有利的；柠檬酸／硝酸盐的摩尔比是影响YVO₄：Eu³⁺纳米晶的颗粒特征、发光强度的一个重要因素，获得最高发光强度的摩尔配比是5／2；共掺杂Li⁺可以大大提高YVO₄：Eu³⁺纳米晶的发光强度，同不加入Li⁺的样品相比，加入5mol％Li⁺的样品的发光强度增加了11倍。②采用沉淀法制备了YVO₄：Er³⁺和YVO₄：Er³⁺，Mn²⁺纳米晶，研究表明，由于浓度猝灭的影响，当Er³⁺掺杂浓度为0.3mol％时，YVO₄：Er³⁺样品553nm主发光峰的发光强度最强；随着退火温度的升高，颗粒的结晶度越来越好，YVO₄：Er_0.003³⁺样品的发光强度越来越高；由于从Mn²⁺到Er³⁺存在着有效的能量传递，使得YVO₄：Er_0.003³⁺，Mn_0.001²⁺样品的发光强度是YVO₄：Er_0.003³⁺发光强度的1.5倍。③采用沉淀法制备了不同形貌及尺寸的LaVO₄：Eu³⁺纳米晶，研究表明：反应pH值是影响LaVO₄：Eu³⁺纳米晶的形貌及颗粒尺寸的重要因素，而形貌及颗粒尺寸的差异又导致LaVO₄：Eu³⁺纳米晶发光强度的不同；在LaVO₄：Eu³⁺纳米晶中，Eu³⁺的荧光猝灭浓度为3mol％；由于存在Eu³⁺→Dy³⁺非辐射能量传递，在LaVO₄：Eu³⁺纳米晶中共掺进Dy³⁺后，Eu³⁺的发光强度反而降低了。随着应用领域的增多，对荧光粉体的需求量也急剧增加，而以各种稀土材料为基质的荧光粉体的成本较高，这就需要寻找相对低廉的新材料来代替它们。由于碱土金属钒酸盐热稳定性高、结晶性和可见光透过性好，因此有可能是一种比较合适的发光基质。在第三章中，首次采用柠檬酸溶胶-凝胶燃烧法成功制备了以碱土钒酸盐（Ca₃（VO₄）₂、Sr₃（VO₄）₂）为基质的纳米发光材料并研究了其发光特性。对于Ca₃（VO₄）₂：Eu³⁺发光材料，最佳退火温度是750℃，此温度下制备的Ca₃（VO₄）₂：Eu³⁺的发光强度略大于同样的合成条件下制备的稀土钒酸盐YVO₄：Eu³⁺的发光强度；在Ca₃（VO₄）₂基质中，Eu³⁺的猝灭浓度为6mol％；当共掺Mn²⁺时，由于存在Eu³⁺→Mn²⁺的能量传递，Eu³⁺在Ca₃（VO₄）₂基质中的发光强度急剧降低。对于Sr₃（VO₄）₂：Eu³⁺发光材料，由于高的退火温度导致颗粒的团聚，Sr₃（VO₄）2：Eu³⁺的发光强度随退火温度的升高而降低；柠檬酸／硝酸盐的摩尔比是影响Sr₃（VO₄）₂：Eu³⁺的颗粒特征、发光强度的一个重要因素，获得最高发光强度的摩尔配比是6／3；加入适量的硼酸助熔剂可以提高Sr₃（VO₄）₂：Eu³⁺的发光强度，同不加入硼酸的样品相比，加入5mol％硼酸时所制备样品的发光强度增加了1.5倍。由于材料的性能与形貌有很大的关系，因此设计能对材料的形貌进行控制的合成方法一直是材料研究领域的重要课题。在第四章中，我们首次采用表面活性剂辅助的水溶液法制备了长棒状、近圆球状等不同形貌及大小的Pb₅（VO₄）₃OH纳米晶并对其形成机理和发光特性进行了研究。由于阴离子表面活性剂十二烷基苯磺酸钠（SDBS）和阳离子表面活性剂十二烷基二甲基苄基溴化铵（DDBAB）在溶液中所形成胶团的形状和大小、所带电荷及立体化学性质不同，造成在添加不同表面活性剂的溶液中所形成纳米晶的形貌及大小不同。Pb₅（VO₄）₃OH样品位于601nm处的发光峰来源于铅离子的³P₁-¹S₀跃迁，而且晶粒的形态和大小影响到样品的发光效率。在环境污染治理技术中，可以利用太阳能降解有机污染物的半导体光催化技术被认为是净化环境的技术革命。随着全球性的环境污染日趋严重，开发新型半导体光催化剂和光催化剂的固载问题日益成为人们的研究热点。在第五章中，我们选择钛酸铋系氧化物(Bi₁₂TiO₂₀、Bi₄Ti₃O₁₂、Bi₂Ti₂O₇)为研究对象，采用化学溶液分解法（CSD）制备了钛酸铋系列薄膜并研究了其光催化性能。①首次采用CSD法制备了具有高光催化活性的软铋矿型Bi₁₂TiO₂₀薄膜。研究表明，500℃退火15分钟制备的涂膜层数为4的Bi₁₂TiO₂₀薄膜光催化活性最高，紫外光照射2h后，其对甲基橙的降解率就高达94％。此外，CSD法制备的Bi₁₂TiO₂₀薄膜具有较好的抗失活稳定性，且在载玻片上附着性良好，显示出极好的应用前景。②制备了铋系层状钙钛矿型Bi₄Ti₃O₁₂和(Bi_1-xLa_x)₄Ti₃O₁₂薄膜，并首次系统研究了其光催化性能。研究表明，550℃退火15分钟制备的4层Bi₄Ti₃O₁₂薄膜光催化活性最高。La³⁺掺杂可以提高Bi₄Ti₃O₁₂光催化薄膜的活性，La³⁺的最佳掺杂浓度是20at％。紫外光照射2h后，(Bi_0.8La_0.2)₄Ti₃O₁₂薄膜对甲基橙的降解率为83％。另外，XRD和AFM结果显示La³⁺在(Bi_1-xLa_x)₄Ti₃O₁₂薄膜的退火过程中起到晶粒生长抑制剂的作用。③制备了烧绿石型Bi₂Ti₂O₇薄膜和La掺杂的钛酸铋（BLT）薄膜，并首次系统研究了它的光催化性能。研究表明，550℃退火30分钟制备的6层Bi₂Ti₂O₇薄膜光催化活性最高；La³⁺掺杂能促进钛酸铋从烧绿石相到层状钙钛矿相的相转变，因此La³⁺可被认为是层状钙钛矿相的稳定剂；La³⁺掺杂可以提高Bi₂Ti₂O₇光催化薄膜的活性，La³⁺的最佳掺杂浓度是5at％，紫外光照射2h后，BLT薄膜对甲基橙的降解率为61％。另外，XRD和AFM结果显示La³⁺在BLT薄膜的退火过程中也起到晶粒生长抑制剂的作用。在第六章中，我们对本论文的工作进行了总结。更多还原

【Abstract】 This dissertation includes two parts. The first part involves the studies on preparation, characterization and photoluminescence performance of Vanadate Nanomaterials. This is the main content of this dissertation. The second part is focused on the studies on preparation, characterization and photo-catalytic performance of bismuth titanate series thin films.Luminescence materials have found wide applications in many fields, such as display, illumination and photo-electronic devices. With the rapid development of nanotechnology, nanoscaled luminescence materials have drawn much attention and been the hot topic because these materials have many miraculous properties compared with the bulk materials. Vanadates have excellent thermal and chemical stability. Their luminescence properties, however, have not drawn enough attention. In order to explore novel luminescence systems with high efficiency, in this thesis, we synthesized vanadate nanomaterials via different methods and studied their luminescence properties systemically.In Chapter 1, we briefly illustrated the corresponding luminescence theory of solids, the preparation methods and the unique properties of nanomaterials and nanosized luminescence materials. The research progress in the field of nanosized vanadate luminescence materials was also summarized.In Chapter 2, we studied the synthesis and characterization of nanosized rare earth vanadate （YVO₄ and LaVO₄） luminescence materials. （1）YVO₄: Eu³⁺ nanocrystals with different sizes have been synthesized via a citric acid sol-gel combustion method using citric acid as a fuel/reductant and nitrates as oxidants. Their PL properties have been also systematically studied. The influence of processing conditions, such as the calcination temperature, the citric acid/nitrates molar ratio and the amounts of lithium nitrate （LiNO₃） additive, on the powder characteristics and fluorescence properties of the resultant yttrium orthvanadate doped with 5mol% Eu³⁺ have been investigated. From the results, we can conclude: The emission intensity of Eu³⁺ in YVO₄: Eu³⁺ increases with the increasing of the calcination temperature （T）, which shows that high calcination temperature is favorable for high luminescence intensity of the samples within nanometer scale. The citric acid/nitrates ratio （9） is a predominant factor for the growth of YVO₄: Eu³⁺ nanocrystals with different particles sizes, which affects their PL emission intensity greatly. The optimumφis 5/2 for the highest luminescence intensity. The luminescence intensity of this compound is enhanced remarkably by the incorporation of Li⁺ ions. The luminescence intensity of YVO₄: Eu³⁺ with addition of 5mol% Li⁺ ions increases as much as 11 times compared with the Li⁺ ions-free YVO₄: Eu³⁺ sample. （2）YVO₄: Er³⁺ and YVO₄: Er³⁺, Mn²⁺ nanocrystals have been synthesized by precipitation means and the luminescence properties have been investigated systematically. The following conclusions can be obtained from our study: The emission intensity of Er³⁺in the YVO₄ host at 553 nm can reach the optimum value when the concentration of Er³⁺is 0.3 mol%, which is a result of concentration quenching. The crystallinity of YVO₄ particles improves gradually with increasing the annealing temperature, which leads to the increasing of the PL intensity of YVO₄: Er³⁺o.oo3 samples. As the energy transfer from Mn²⁺ to Er³⁺ exists, the PL intensity of YVO₄: Er³⁺_0.003, Mn²⁺_0.001 is about 1.5 times of that of YVO₄:Er³⁺_0.003 （3） LaVO₄:Eu³⁺ nanocrystals with different sizes and morphologies have been synthesized via a precipitation method. The PL properties have also been systematically studied. From the results, we can conclude: The reaction pH is a predominant influencing factor for the growth of LaVO₄: Eu³⁺ nanocrystals with different sizes and morphologies, and their sizes and morphologies affect their PL emission intensities evidently. The emission intensity is highly dependent on the dopant concentration and the optimum concentration of dopant is 3mol%. The emission intensity of Eu³⁺ in LaVO₄ matrix is lowered after co-doped with Dy³⁺ due to the energy transfer from Eu³⁺ to Dy³⁺.In Chapter 3, we studied the combustion synthesis and characterization of nanosized alkaline earth vanadate （Ca₃（VO₄）₂ and Sr₃（VO₄）₂） luminescence materials. Ca₃（VO₄）₂:Eu³⁺, Mn²⁺ powders with different sizes and morphologies have been synthesized via a citric acid sol-gel combustion method using citric acid as a fuel/reductant and nitrates as oxidants. The PL properties have been also systematically studied. The optimized annealing temperature is 750℃in the present case. The emission intensity at 613 nm of Eu³⁺ in the Ca₃（VO₄）₂ host can reach the optimum value when the concentration of Eu³⁺ is 6 mol%, because of the existence of concentration quenching. The emission intensity of Ca₃（VO₄）₂: Eu³⁺, Mn²⁺ decreases owing to the energy transfer from Eu³⁺ to Mn²⁺. Sr₃（VO₄）₂: Eu³⁺ nanocrystals with different sizes and morphologies have also been synthesized via a citric acid combustion method. The effects of processing parameters, such as the molar ratio of citric acid to nitrates （φ）, calcination temperature （T） and the amounts of the additive boric acid HBO₃ （B） on the powder characteristics and fluorescence properties of the resultant Sr₃（VO₄）₂ doped with 5% Eu³⁺ have been investigated. From the results, we can conclude: The molar ratio of citric acid to nitrates （φ） is a predominant influencing factor for the growth of Sr₃（VO₄）₂: Eu³⁺ nanocrystals with different particle sizes and emission intensities evidently. The optimumφis 6/3 for the highest luminescence intensity. The emission intensity of Sr₃（VO₄）₂ : Eu³⁺ decreases with the increasing of the calcination temperature （T）, owing to the falling of the specific surface areas. The optimum addition amount of boric acid is 5 mol% of the total reagent. The emission intensity of Sr₃（VO₄）₂: Eu³⁺ increases 1.5 times compared with the particles prepared without the additive.In Chapter 4, rod-like or spherical Pb₅（VO₄）₃OH nanocrystals have been successfully prepared through a precipitation process in the presence of sodium dodecylbenzenesulfonate （SDBS） or dodecyldimethylbenzylammonium bromide （DDBAB）, respectively. The effect of ion-surfactants in the formation process of nanocrystals may be correlated with the charge and stereochemistry properties of the surfactants. The 601 nm emission of the Pb₅（VO₄）₃OH nanocrystals is ascribed to the ³P₁-¹S₀ transition of Pb²⁺ ions. As one of the novel pollutant treatment method, photocatalysis gains more and more attentions in the field of environmental purification. Developing new photocatalysts and the supported technique of photocatalysts have always been the hot topic of the researchers. In Chapter 5, we chose bismuth titanate (Bi₁₂TiO₂₀ Bi₄Ti₃O₁₂ and Bi₂Ti₂O₇) as the study target, prepared bismuth titanate series thin films by CSD（chemical solution decomposition） method and systematically examined their photocatalytic performance. （1）Sillenite Bi₁₂TiO₂₀ thin films with high photocatalytic activity have been firstly prepared. When annealed at 500℃for 15 minutes, the prepared sample with 4 coatings exhibits the highest photocatalytic activity. After irradiation for 2 h, the methyl orange solution is degraded by 94% on the Bi₁₂TiO₂₀ thin films annealed at 500℃for 15 minutes. Moreover, Bi₁₂TiO₂₀ thin films prepared by CSD method show a good anti-inactivation stability and adhere well on the silicate substrate after they have been used for many times. （2）Bi₄Ti₃O₁₂ and (Bi_1-xLa_x)₄Ti₃O₁₂ with bismuth-layered perovskite structure thin films were successfully prepared and their photocatalytic properties have been firstly investigated. When annealed at 550℃for 15 minutes, the prepared Bi₄Ti₃O₁₂ thin films by 4 coating cycles exhibited the highest photocatalytic activity. La³⁺ doping could improve the photocatalytic activity of Bi₄Ti₃O₁₂ thin films. An optimal La³⁺ dopant amount for (Bi_1-xLa_x)₄Ti₃O₁₂ thin films is 20 at%. After irradiation for 2h, the methyl orange solution was degraded by 83% on the (Bi_0.8La_0.2)₄Ti₃O₁₂ films. Additionally, substituted La³⁺ ions can act as a grain-growth inhibitor in perovskite (Bi_1-xLa_x)₄Ti₃O₁₂ thin films. （3）Dopant-free Bi₂Ti₂O₇（BT） thin films with pyrochlore structure and La-doped bismuth titanate （BLT） thin films were successfully prepared and their photocatalytic properties were firstly investigated. When annealed at 550℃for 30 minutes, the prepared BT thin films by 6 coatings cycles exhibited the highest photocatalytic activity. La³⁺ doping could improve the photocatalytic activity of BT thin films. An optimal La³⁺ dopant amount for BLT thin films is 5 at%. After irradiation for 2 h, the methyl orange solution was degraded by 61% on the BLT films annealed at 550℃for 30 minutes. In addition, substituted La³⁺ ions can act as a stabilizer of perovskite BLT and a grain-growth inhibitor in BLT thin films.In Chapter 6, a concise summary of our work was given.更多还原