【作者】 韩梅；

【导师】 冯守华；

【作者基本信息】 吉林大学 ， 无机化学， 2018， 博士

【摘要】 结构与性质之间的关系是固体化学重要的研究内容之一,基于对两者之间关联现象的研究,分析两者之间的作用机制,通过调节化合物的分子组成、晶体结构、微观结构及电子结构等因素,改变或定向调节化合物的某些性质,以期达到预期的效果,使化合物材料化、功能化。无机氧化物具有丰富的组成、结构和性质,一直是固体化学、固体物理、材料化学等学科研究的物质宝库。特别是无机氧化物的制备方法多样、组成结构丰富、性质优异、应用广泛。通过研究不同制备方法对氧化物宏观形貌和微观结构的调控,进而考证其对光、电、磁等物理性质的影响具有重要的科学研究价值和实用意义。尖晶石氧化物是一类重要的无机矿物质,自然界中矿藏丰富、人工合成技术成熟多样,是一种在工业上得到广泛应用的材料。尖晶石氧化物的标准化学组成为AB₂O₄,其中二价金属元素A占据1/8的四面体位置（T_d）,三价金属元素B占据半数的八面体位置（O_h）,两者之间可以存在一定异位取代。这样就使得尖晶石氧化物具有尖晶石、反尖晶石、混合型尖晶石三大结构类型。结构的多样性和组成元素的丰富性使得尖晶石类氧化物呈现出异常复杂的性质。尖晶石铝酸盐结合了尖晶石结构和铝酸盐两者的优良性质,具有耐高温、高硬度、耐酸碱等特性,根据A位二价碱土金属或过渡金属元素的不同,可作为优良的光催化剂、过渡层材料、颜料、荧光材料和耐火材料使用。合成尖晶石氧化物常用的方法有:高温固相合成方法、溶胶-凝胶法、共沉淀法、水热合成方法及溶液燃烧方法等。本论文课题的研究首先基于对尖晶石铝酸盐的制备技术的研究,选取溶液燃烧法合成样品并制备出了多个不同组分的尖晶石铝酸盐化合物,详细的测试和分析了这些化合物的结构与相关性质。在此基础上,进而将结构调控与溶液燃烧法结合,聚焦在MgAl₂O₄:Eu³⁺化合物的荧光性质调控研究上,取得了以下结果:1.通过溶液燃烧法制备了MgAl₂O₄,CoAl₂O₄,NiAl₂O₄,CuAl₂O₄和ZnAl₂O₄粉体样品,对其进行了结构和物理性质表征。利用甘氨酸作为燃烧剂,使用硝酸铝、碱土金属硝酸盐、过渡金属硝酸盐作为反应原料。按照产物的摩尔计量比配制溶液,在400℃条件下发生自烧燃反应,通过溶液瞬时燃烧产生的高温合成样品。然后再通过进一步的高温煅烧除去样品表面的积碳,并使样品进一步晶化。产物MgAl₂O₄和ZnAl₂O₄为白色粉末样品。CoAl₂O₄、NiAl₂O₄和CuAl₂O₄则为分别为蓝色、浅绿及棕色粉体。XRD分析产物为高结晶度的纯相尖晶石氧化物,扫描电镜显示产物为纳米粒子堆积而成的粉体。通过进一步的XPS分析,样品的尖晶石结构中存在一定的反位掺杂现象。根据A位元素的离子半径不同,这种异位掺杂体现一定的规律性:当A位离子与Al³⁺离子的半径接近时,非常容易发生异位掺杂。我们进一步对含有磁性离子的CoAl₂O₄、NiAl₂O₄和CuAl₂O₄样品进行了磁性和比热性质的测试。通过磁性测试分析,CoAl₂O₄和CuAl₂O₄样品表现出很强的磁阻挫现象,这也符合CoAl₂O₄和CuAl₂O₄的几何阻挫结构特征。而NiAl₂O₄体现了反铁磁性质。通过低温比热测试分析,得出了和磁性数据分析相同的结论,并进一步给出各个样品的迪拜温度参数、爱因斯坦温度参数和磁熵变数值。这些有助于我们加深对以上化合物结构和性质的认识。2.在对溶液燃烧法制备尖晶石铝酸盐的前期研究基础上,我们发现使用该方法制备的金晶石化合物具有较强的结构容忍能力,比较容易进行异质元素的取代。因此我们针对荧光化合物MgAl₂O₄:Eu³⁺进行了调控实验,重点考察了不同的二次煅烧温度对样品结构和性质的影响。XRD和低温比热测试显示样品随着二次处理温度的提升结晶度和结构刚性明显提升。SEM电镜显示溶液燃烧法合成的样品为小颗粒聚集而成的海绵状结构,其孔道是由于燃烧时产生的大量气体造成的。随着二次处理温度的增加,这种孔道变得密集。对样品的荧光性质表征显示,所有样品都可以被274 nm和394 nm的紫外光激发,下转换发射613 nm红光。并且394 nm激发的发射光强度明显高于274 nm激发的发射光。不同温度处理的样品中,900℃处理的样品表现出最佳的发光性质。这说明通过溶液燃烧制备的样品的发光性质,不仅仅依赖于材料整体的晶化程度和结构刚性,更需要Eu³⁺离子掺杂点（局部无序）和整体结构（长程有序）之间达到某种平衡才有利于发光效率的提升。3.笔者在尝试使用水热合成方法制备尖晶石氧化物的过程中,意外的获得了一种新型结构的AgCu（IO₃）₃碘酸盐单晶化合物。对其进行的单晶结构解析表明这种AgCu（IO₃）₃化合物与AgPb（IO₃）₃同构,晶体由两个John-Teller畸变的八面体CuO₆,三个金字塔型IO₃和一个不规则多面体AgO₇构成三维结构。晶体结构中含有一个由CuO₆八面体共顶角链接构成的z型链。磁学性质测试和分析显示化合物的类一维磁性链中存在铁磁相互作用和反铁磁相互作用,并在宏观上表现为弱的反铁磁性质。关于这部分的研究结果在论文中一并给出。本论文以研究功能氧化物的制备和性质为目的,摸索了制备氧化物的实验合成方法对结构和物理性质的影响,探讨了制备方法、结构与性质之间的关系,得到了一些新颖的结果。在此过程中丰富了合成与制备化学的科学内涵,也为固体化学的发展提供了新的研究视角和研究材料。更多还原

【Abstract】 The relationship between structure and properties of a compound is an important topic in solid state chemistry.Based on the research in this relationship and analysis of the inside mechanism,researchers can adjust the parameters of composition,crystal structure,microstructure and electron structure,to change or tune properties of a compound.A compound with some remarkable property can be taken as a functional material.Oxides have rich composition,structure,and property,which is a main subject to many disciplines like solid state chemistry,solid state physics,and material chemistry etc.Considering the various preparation methods,rich composition,remarkable properties and wide application of oxides,it is both academic and applied significance to tune the morphology and micro-structure of an oxide to evaluate the optical,electrical,and magnetic properties.Spinel oxide is an important industrial material,which is land mineral-rich and preparation diversity.Transition metal oxides with spinel structure AB₂O₄,where A occupies one-eighth of the tetrahedral sites（T_d）and B occupies half of the octahedral sites in a face-centered cubic close-packed oxygen sublattice（O_h）.Besides the normal spinel structure,the structure can be defined as inversed spinel structure if the divalent cations fully occupy on O_h sites or mixed spinel structure once the divalent partly occupy on O_h sites.Diversity of structure and composition make the properties complicated.Spinel aluminates take the advantage of spinel structure and chemical composition,showing characters of high temperature tolerance,high hardness,acid and base tolerance.Depending on the alkaline earth or transition element in A site,Spinel aluminates are used as photocatalysts,buffer layers,pigments,phosphors,refractories.There are many methods to prepare the spinel aluminates:solid state method,sol-gel,co-precipitation,hydrothermal technology,and solution combustion method,etc.We studied various preparation method for spinel oxides and choose the solution combustion method to prepare the spinel aluminates.Several spinel aluminates were prepared,which’s structure and property were further characterized.Combined the structural adjustion and solution combustion method,we focus on the luminance property of MgAl₂O₄:Eu³⁺phosphor and gain the following results.（1）A series of spinel aluminate nanopigments（MgAl₂O₄,CoAl₂O₄,NiAl₂O₄,CuAl₂O₄,and ZnAl₂O₄）were synthesized with an easy solution combustion method and the structure and property were characterized.An aqueous solution containing stoichiometric amount of nitrates and glycine as fuel is heated above 400℃rapidly,then the solution boils and burns.The compound is formed during the combustion process due to the flashily released heat.As-prepared combustion products need secondary heat treatment to further crystallize and remove the carbon deposition.MgAl₂O₄ and CoAl₂O₄ are formed as white powder;the CoAl₂O₄ is blue;NiAl₂O₄ is light green;CuAl₂O₄ is brown.From the XRD patterns,no impure phases are observed and all these as-prepared samples are crystalized in the designed spinel phase.SEM show all the samples were composed by aggregated nanoparticles with the character of porous structure.XPS analysis suggests that the Al³⁺cations occupy these two different positions due to site inversion effect.It seems that the Al³⁺cations are more easily to occupy the O_h sites if the radius of the divalent metal cations are close to that value of Al³⁺in the combustion method.The magnetic properties of CoAl₂O₄,NiAl₂O₄,and CuAl₂O₄ were characterized.Both CoAl₂O₄ and CuAl₂O₄show frustrated magnetic property.However,NiAl₂O₄ show antiferromagnetic property.Heat capacities of these compounds are further studied and evidence the strong spin frustration in CoAl₂O₄ and CuAl₂O₄,which give the corresponding Debye temperature,Einstein temperature,and magnetic entropy.It helps us to better understand the relationship between structure and property of these spinels.（2）Base on the work mentioned above,we found the spinel structure has strong tolerance for foreign element doping.To investigate the influence of annealing temperature on the structural rigidity and photoluminescence,Eu³⁺doped MgAl₂O₄ceramics have been synthesized by a solution combustion reaction and thermally treated at various temperature.Powder XRD indicate that pure spinels were synthesized and the crystallinity increased with the increase of the heat treatment temperature.Low temperature heat capacities of sample show the structural rigidity has positive relationship with the calcine temperature.The SEM show spongy structure of the particles formed due to the exhausting the large amount of gases during the short solution combustion process.The porosity increased with the rise of the secondary treatment temperature.These phosphors exhibit hypersensitive red emission peaking at 613 nm when excited by 274 nm and 394 nm light.Moreover,the emission excited by 394 nm is stronger than that excited by 274 nm.The MgAl₂O₄:Eu³⁺calcined at 900℃shows the best performance and the effective emission excited by near-UV 394 nm.The photoluminescence not solely depends on the structural rigidity but needs some balance between the disorder caused by Eu³⁺doping and long range order of the structure.（3）During the research on hydrothermal preparation of spinel oxides.A new complex AgCu（IO₃）₃ is synthesized and characterized by single crystal X-ray diffraction and magnetization measurement.AgCu（IO₃）₃ is isostructral with AgPb（IO₃）.The crystal structure of AgCu（IO₃）₃ consists of two crystallographically distinct distorted octahedral CuO₆ groups,three different pyramidal IO₃ groups and an irregular AgO₇ polyhedron.The Cu（1）O₆ and Cu（2）O₆ octahedra alternate and share a common oxygen corner O（1）to form a zigzag chains.The magnetization data suggests the weak antiferromagnetic interaction dominates the magnetic property of the compound,although there are coexistence of antiferromagnetic interaction and ferromagnetic interaction.By studying the structure and properties of functional oxide,this paper explores the experimental methods to control the physical properties of materials and further discusse the relationship among the preparation,structure,and property.This experimental results enrich the inorganic synthesis and preparative chemistry and also provide some new viewpoints and experimental cases for the development of solid state chemsitry.更多还原