【作者】 黄新友；

【导师】 陈志刚；

【作者基本信息】 江苏大学 ， 材料学， 2008， 博士

【摘要】 以（Ba，Sr）TiO₃为基（简称为BST），采用传统电容器陶瓷制备工艺和常规电容器陶瓷原料，借助正交设计法研究各种掺杂助剂的种类和用量对中温烧结BST基电容器陶瓷介电性能的影响，确定了影响中温烧结的BST基陶瓷介电性能的主次因素，其性能随各因素水平影响的趋势，得到最佳配方。在正交实验的基础上用单因素变量法研究铅硼玻璃、Bi₂O₃／Li₂O固溶体、CaZrO₃、Nb₂O₅／Co₂O₃及其加入量对（Ba，Sr）TiO₃基陶瓷中温烧结、性能以及结构的影响，研究其作用机制，认为4PbO．B₂O₃、Bi₂O₃／Li₂O固溶体在烧结过程中形成液相，使得晶粒发生重排，强化晶粒接触，气孔充分排出，促进晶粒发育，提高瓷体致密度，从而达到降低烧结温度的目的，并通过成分起伏相变影响瓷料的介电温度特性，添加不同量的CaZrO₃对瓷料的改性机理不一，掺杂少量CaZrO₃使得样品发生叠峰现象，提高样品的介电常数，掺杂过量的CaZrO₃则是通过固溶缓冲展宽机制和粒界缓冲展宽机制影响瓷料的介电性能。掺杂Nb₂O₅和Co₂O₃的压峰和展宽作用较为明显，分析其原因是形成了壳一核结构，限制晶粒长大。讨论分析了各掺杂物的作用机理。采用传统工艺和常规原料制备电容器陶瓷，通过调整配方和工艺，得到一系列中温烧结介电性能优良的BST电容器陶瓷配方。采用正交设计实验、Bi₄Ti₃O₁₂单因素变量法掺杂实验、Dy₂O₃单因素变量法掺杂实验研究了各组分对高压X7R特性钛酸钡锶基电容器陶瓷介电性能、显微结构和烧结温度的影响，探讨了各组分对钛酸钡锶基电容器陶瓷性能影响机理，为研制高压X7R特性多层陶瓷电容器用介质材料提供了依据。得到介电性能好的晶粒尺寸在1μm左右的高压X7R型中温烧结多层陶瓷电容器用介质材料。CdO的引入有利于Nb₂O₅和Dy₂O₃的固溶和扩散，从而有效的降低了材料的烧结温度，提高材料的介电常数，同时可以改善陶瓷中晶粒的形貌，抑制晶粒的长大。过量的Nb₂O₅偏析于晶界，阻止晶界移动，抑制晶粒生长，从而形成细晶结构。Ca²⁺和Zr⁴⁺分别进入晶格中部分Ba²⁺和Ti⁴⁺位置，都能降低居里点处的介电常数峰值，使居里温度向低温方向偏移，并能抑制晶粒的长大，提高介电常数。Bi₄Ti₃O₁₂玻璃相包裹晶粒和填充粒间，构成瓷体的复杂非均匀结构。异相对BaTiO₃铁电相的制约作用，使B位阳离子所处的势阱深度变浅，表现为ε-T特性曲线较平坦。在钛酸钡基陶瓷中微量掺杂稀土氧化物Dy₂O₃可以抑制晶粒生长，产生细晶效应，使得居里峰在整个工作温区内弥散展宽，获得较高的介电常数和良好的容量温度特性，满足X7R特性，可以大幅度提高钛酸钡锶基陶瓷的耐压强度。在钛酸锶钡基陶瓷中微量掺杂稀土氧化物Y₂O₃可以抑制晶粒生长，产生细晶效应，使得居里峰在整个工作温区内弥散展宽，获得较高的介电常数和良好的容量温度特性，并可以大幅度提高钛酸钡锶基陶瓷的耐压强度。当Y₂O₃掺杂量为0．6wt％和Dy₂O₃掺杂量为1．0 wt％时，分别得到中温烧结综合性能较好的电容器陶瓷。Yb₂O₃的加入没有改变BST陶瓷的晶体结构，大大提高BST陶瓷的介电常数。当Yb₂O₃的加入量为0．9 wt％时，采用碳酸锂作为烧结助剂，得到介电常数高达10000的中温烧结BST电容器陶瓷。MgO掺杂后的样品的介电峰被压抑和展宽，表现出扩散相变。从XRD谱图可知，MgO掺杂后的样品仍为单一的钙钛矿结构。当MgO掺杂量为0．2wt％和1．0wt％时，分别得到综合性能较好的中温烧结的钛酸钡锶陶瓷。Bi₂Sn₂O₇掺杂物包裹晶粒和填充晶粒间，构成瓷体的复杂非均匀结构。这种异相对（Ba,Sr）TiO₃铁电相有制约作用，使B位阳离子所处的势阱深度变浅，表现为ε-T特性曲线较平坦。当Bi₂Sn₂O₇掺杂量为30wt％时，得到综合性能好的符合X7R特性烧结温度为1150℃的中温烧结钛酸钡锶陶瓷。在Ba（CH₃COO）₂-Sr（NO₃）₂-Cd（NO₃）₂-Ti（OC₄H₉）₄-H₂O-CH₃COOH-CH₃CH₂OH体系中，采用溶胶凝胶法研究了(Ba_0.70Sr_0.25Cd_0.05)TiO₃（BSCT）超细粉体的制备。采用x-射线衍射仪和比表面积测定仪研究了加水量、热处理温度等对BSCT纳米粉体的颗粒尺寸、物相组成和比表面积的影响，用扫描电镜和透射电镜观察了BSCT纳米粉体的颗粒尺寸和形貌。得到多层陶瓷电容器用BSCT纳米粉体，粉体的平均粒径为80nm左右，比表面积为13．64m²／g。干凝胶经过950℃热处理即可形成钙钛矿相，比传统固相合成法低250℃～300℃。采用溶胶-凝胶法制备的(Ba_0.70Sr_0.25Cd_0.05)TiO₃超细粉体研究了(Ba_0.70Sr_0.25Cd_0.05)TiO₃超细陶瓷的制备，其平均晶粒尺寸约为1μm；得到综合性能较好的(Ba_0.70Sr_0.25Cd_0.05)TiO₃超细陶瓷。随着晶粒尺寸的减小，(Ba_0.70Sr_0.25Cd_0.05)TiO₃陶瓷材料介电常数峰值有大幅度的提高，相变温区有变窄趋势。采用柠檬酸-硝酸盐燃烧法研究了超细钛酸钡锶（BST）粉体和掺杂BST粉体的制备；研究了柠檬酸量、溶液的PH值、热处理温度和分散剂对超细BST粉体的物相和形貌及颗粒大小的影响，确定了最佳的柠檬酸量、PH值、热处理温度和分散剂（乙二醇）的量。得到超细BST粉体，其相结构为立方相钙钛矿结构，平均粒径约为50-100nm，颗粒形貌为不规则球形。同时还得到掺杂的超细BST粉体，平均粒径约为70nm。采用溶胶-凝胶法研究了Bi₄Ti₃O₁₂粉体的制备，得到的超细Bi₄Ti₃O₁₂粉体相结构为铋层状结构，粒径约为70nm左右。在超细BST粉体及含有Mn、Mg、Zn、Y和Co掺杂的BST粉体中掺杂超细Bi₄Ti₃O₁₂粉体制备了混合BST粉体。利用BST混合粉体进一步研究了超细晶BST陶瓷的制备。研究了烧结温度、Bi₄Ti₃O₁₂掺杂量和微量元素掺杂对超细晶BST陶瓷表面显微结构和介电性能的影响。得到了具有好的介电性能超细BST电容器陶瓷，其烧结温度为1200℃和1150℃，陶瓷的平均粒径为0．5μm。更多还原

【Abstract】 The traditional preparation method and the conventional raw materials of capacitor ceramics have been used in these experiments.The influence of different dopants and doping amount on the dielectric properties of medium temperature sintering （Ba,Sr） TiO₃（BST） series capacitor ceramics has been investigated by means of orthogonal design experiments. The major secondary influencing factors and the influencing tendency of various factors levels for the dielectric properties of BST ceramics have been obtained,at the same time ,the optimum formula forε、for tanδand for withstand voltage have been obtained in the experimental conditions.The BST ceramics having optimum comprehensive properties has been obtained by means of orthogonal design experiments。The influencing mechanism of various components on the dielectric properties of BST ceramics is studied.On the basis of orthogonal design experiments, the influence of 4PbO.B₂O₃ glass、Bi₂O₃/Li₂O solid solution CaZrO₃、Nb₂O₅/Co₂O₃ doping amount and Nb/Co ratio on the dielectric properties .structure and medium temperature sintering of （Ba,Sr） TiO₃（BST） series capacitor ceramics has been investigated by means of single factor variable design experiments。The results show that the 4PbO.B₂O₃ and Bi₂O₃/Li₂O solid solution doping can form liquid,arrange crystal grain,make crystal grain contacting,make pore removing, make crystal grain size increasing,enhance ceramics density,and decrease sintering temperature in sintering process.The dielectric constant temperature property is influenced by component increasing and decreasing and phase changing.The doped mechanism is not the same by doping various amount CaZrO₃,little CaZrO₃ doping amount make dielectric peak overlapping phenomenon and increasing dielectric constant of BST ceramics,excessive doping CaZrO₃ amount influence the dielectric properties by means of solid solution cushioning widen mechanism and grain boundary cushioning widen mechanism .The effect of depressing dielectric peak and widening dielectric peak is obvious,this is because of forming core and shell structure and depressing crystal grain growing up.The acting mechanism of dopants doping has also been investigated.A series formulas of medium temperature sintering BST capacitor ceramics with high dielectric performance have been obtained by means of conventional technique and conventional raw materials.With the help of the orthogonal design experiment, the single factor variable experiments doped with Bi₄Ti₃O₁₂ and Dy₂O₃, the influence of various components on the dielectric performance,capacitance temperature characteristic, sintering temperature of barium and strontium titanate（BST） based high voltage capacitor ceramics with X7R specification has been investigated.The influencing mechanism of various components on the dielectric properties of barium titanate based capacitor ceramics is studied. These provide the basis for preparation of BST based capacitor ceramics with high voltage and X7R specification.The capacitor ceramics with good dielectric properties has been obtained,which the size of crystal grain is about 1μm, the sintering temperature is 1120℃, the capacitance temperature property is suited for X7R,dielectric constant e is 1324.2, dielectric loss is 0.0070, the withstand voltage is larger than 10kv/mm,.Doping CdO helps Nb₂O₅ and Dy₂O₃ dissolve and diffuse, reducing material’s sintering temperature effectively, raising dielectric constant improving the shape look of crystal grain of ceramics, restraining crystal grain from growing up. Excessive Nb₂O₅ segregates in crystal boundary, preventing crystal boundary from moving, restraining the growth of crystal grain, thus forming fine grain structure. Ca²⁺ and Zr⁴⁺ respectively enter into some Ba²⁺ and Ti⁴⁺ location in the crystal lattice, reducing the dielectric constant peak value in the curie point, making curie temperature moving towards low temperature, restraining crystal grain growing up ,elevating dielectrical constant.Bi₄Ti₃O₁₂ glass phases parcel crystal grain and are filled with between grains, forming the complex and not even structure of ceramic body. Different phases restricts barium titanate ferroelectric phases, making the depth of potential well of B position cation change shallow,and showing dielectric constant（ε） temperature（T） characteristic curve rather smooth.In BST based ceramics, doping small rare earth oxide Dy₂O₃ can keep back the growth of crystal grain, producing fine grain effect, making curie summit in entire work temperature range scatter and spread, get higher dielectric constant and good capacity temperature property,satisfy X7R property, raising the withstand voltage of BST based ceramics greatly.In barium-strontium titanate based ceramic, doping small amount rare earth oxide Y₂O₃ can keep back the growth of crystal grain, producing fine grain effect, making curie summit in entire work temperature range scatter and spread, get higher dielectric constant and good capacity temperature property, raising the withstand voltage of barium strontium titanate based ceramic substantially. When Y₂O₃ doping amount is 0.6wt% and Dy₂O₃ doping amount is 1.0 wt%, the medium temperature sintering BST ceramics with good dielectric properties has been obtained respectively.X-ray diffraction analysis shows that the crystal structure of barium-strontium titanate ceramics is not affected by Yb₂O₃ doping. The dielectric constant of barium-strontium titanate ceramics become elevating greatly while Yb₂O₃ doping. When Yb₂O₃ doping amount is 1.2wt%, the BST capacitor ceramics with high dielectric constant has been obtained ,which dielectric constant is 10000 and dielectric loss is 0.021.The temperature dielectric constant temperature peak is depressed and broadened while MgO doping. XRD paterns show that a single perovskite phase in samples. When MgO doping amount is 0.2wt% and 1.0 wt%,the BST ceramics with good comprehensive dielectric properties has been obtained respectively.The results show that Bi₂Sn₂O₇ parcel crystal grain and are filled between grains, forming the complex and not even structure of ceramics. Different phases restricts barium-strontium titanate ferroelectric phases, making the depth of potential well of B position cation change shallow and showing dielectric temperature characteristic curve rather smooth. When Bi₂Sn₂O₇ doping amount is 30wt%, the BST ceramics with good comprehensive dielectric properties has been obtained,which is suitable for X7R and sintered at 1150℃.Nanometer (Ba_0.7Sr_0.25Cd_0.05)TiO₃ （BSCT） powder is prepared by sol-gel method from Ba（CH₃COO）₂-Sr（NO₃）₂-Cd（NO₃）₂-Ti（OC₄H₉）₄-H₂O-CH₃COOH-CH₃CH₂OH system. The influence of water volum and heat treatment temperature on the particle size .material phase composition and specific surface area of the BSCT nanometer powder was investigated using x-ray diffraction and specific surface area measurement instrument.The nanometer BSCT powder used for multilayer ceramic capacitor has been obtained,which The average particle size of the powder is 80 nm , the specific surface area is 13.64m²/g .Heat treatment at 950℃can form perovskite strucrure,which is low 250℃-300℃than traditional solid phase synthesis.The (Ba_0.7Sr_0.25Cd_0.05)TiO₃ superfine ceramics which the grain size is approximately 1μm are prepared using (Ba_0.7Sr_0.25Cd_0.05)TiO₃ namometer powder. The superfine BSCT ceramics with good comprehensive dielectric properties has been obtained. With decreasing of the grain size,phase changing temperature region decreases greatly, while the maximum dielectric constant increases greatly.The ultra-fine BST powders and doped ultra-fine BST powders prepared by citrate-nitrate combustion method were studied. The influence of citrate acid volume、pH value、heat-treating temperature and dispersant（ethylene alcohol） volume on the material phase ,morphology and particle size of ultra-fine BST powders were investigated, to obtain the optimum amount of citrate acid volume and dispersant（ethylene alcohol） volume, the proper pH value and heat-treating temperature. The superfine BST powders was obtained ,which the phase structure of BST powders is cubical phase, the average grain size is about 50-100nm,the particle morphology is irregularity spherical shape with conglobationAt the same time , the doped ultra-fine BST powders was obtained, the average grain size is about 70nm.Ultra-fine Bi₄Ti₃O₁₂ powders were prepared by Sol-gel method . The results indicate that the phase structure of Bi₄Ti₃O₁₂ powders is bismuth layer-structure and the average grain size is 70nm.BST mixed-powders were prepared by ultra-fine BST powders and doped BST powders doped with ultra-fine Bi₄Ti₃O₁₂ powders. The preparation of superfine BST ceramics using BST mixed powders was studied. The surface topography, microscopic structure and phase structure of ultra-fine BST ceramics were analysed systematically. The effects of sintering temperature and the doped amount of Bi₄Ti₃O₁₂ and trace elements doping on the surface microscopic structure and dielectric properties of superfine BST ceramics were studied. The superfine BST capacitor ceramics with good dielectric properties has been obtained ,which the sintering temperature is 1200℃and 1150℃,the grain size is about 0.5μm.更多还原