【作者】 高峰；

【导师】 田长生；

【作者基本信息】 西北工业大学 ， 材料学， 2002， 博士

【摘要】 本文从满足多层片式LC滤波器实际应用的角度出发，将高介弛豫铁电陶瓷与NiZnCu铁氧体叠层低温共烧，研究了两类材料的共烧兼容特性，提出共烧兼容体系材料的设计原则，揭示出弛豫铁电陶瓷与铁氧体共烧界面反应及相组织形态和微观晶粒形貌的特征与规律，最终获得可低温（900℃）烧结、无分层开裂、无翘曲变形且结合良好的叠层共烧体。 首先根据多层片式LC滤波器的应用要求，从电性能、组成和烧结行为等方面综合分析，提出介电材料的选材原则；根据选材原则，选择0.8Pb(Ni_1/3Nb_2/3)O₃-0.2PbTiO₃（0.8PNN-0.2PT）陶瓷为基体材料，通过添加WO₃和CuO来降低PNN-PT系陶瓷的烧结温度，研究了PNN-PT基陶瓷的相结构和介电性能，获得可低温烧结成瓷，结构致密，室温处于顺电相且容温变化率满足电容器标准的低温烧结介电瓷料用于叠层共烧。 将PNN-PT基低烧陶瓷与(Ni_0.5Zn_0.4Cu_0.10)Fe₂O₄铁氧体（TY-1#）叠层共烧，研究了这两种材料的化学相容性、共烧匹配行为、翘曲变化过程及叠层共烧体（COF1#）的界面显微组织结构。结果表明这两种材料叠层共烧以后产生翘曲缺陷；叠层共烧体中介电体靠近界面处晶粒尺寸大于远离界面处晶粒尺寸，提出差别因子（d_D）用于表征界面处微观组织形态的变化，当烧结温度小于900℃时，差别因子随着烧结温度的增加而减小；当烧结温度大于900℃之后，差别因子随着烧结温度的升高而增大。 从几何学、粘弹性力学和烧结动力学的不同角度出发，探讨了共烧翘曲形成机制和影响因素，建立了介电材料／铁氧体材料叠层共烧翘曲模型和翘曲曲率方程，揭示影响翘曲的因素为形状尺寸因子，材料的烧结特性和异种材料之间的收缩率差，其中烧结过程的收缩率差是翘曲产生的根本因素，收缩率差越大，则翘曲曲率越大。 通过对翘曲影响因素的分析，调整共烧体系，研究了PNN-PT基低烧陶瓷（JD）与(Ni_0.8Zn_0.12Cu_0.12)Fe_1.96O₄铁氧体材料（TY）的烧结动力学，探讨了烧结传质机制，结果表明介电材料的传质机制既有晶格扩散，又有晶界扩散；铁氧体材料的传质机制主要为晶界扩散。由线性回归分析计算出JD材料的烧结激活能为162～174KJ／mol，TY材料的烧结激活能为208～235 KJ／mol。此外还研究了两种材料的烧结收缩行为，并建立了JD材料和TY材料的烧结动力学方程。 研究了900℃下保温时间对JD材料和TY材料相结构的影响，结果表明随着保温时间的延长，介电材料中焦绿石相含量增加，钙钛矿相含量减少；而保温时间对铁氧体材料的相结构无影响；此外，两种材料的晶粒尺寸均随着保温时间的延长而增加，最佳保温时间为2h。 酉北工叱大学博士公位论文一 采用流延工艺将PNN－PT基低烧陶瓷（JD）与（Ni。。ZN；。CUo；。）Fe；。。O。铁氧休村料（＊Y）叠层共烧，研究了叠层共烧体（＊0F3＃）界面显微组织结构和微 观晶粒形貌的特征以及界面结合性能。两种材料于 900 OC下叠层共烧获得了无翘 曲变形的共烧体（COF3＃），叠层共烧体界面均匀连续，结构致密，无气孔或分层厂裂现象；当保温时间小于Zh时，介电体材料靠近界面区域内的晶粒尺寸明 显大于远离界面区域的晶粒尺寸，随着保温时间的增加，靠近界面区域内的晶粒 尺寸与远离界面区域晶粒尺寸的差别逐渐变得不明显，当保温时间超过6．7h时， 差别因子小于1，继续增加保温时间时，界面处晶粒尺寸将小于远离界面区域的 晶粒尺寸。在500℃下淬火后的叠层共烧体界面连接紧密，无分层开裂现象出现， 证实所选择的 JD材料和 TY材料可以良好的共烧在一起，并且能够形成强结合 的界面。 研究了COF3＃叠层共烧体界面处离子扩散行为，根据半无限大互扩散偶模型 对离子扩散层浓度分布进行了数值模拟，模拟曲线与实验结果基本相符：估算了COF3＃叠层共烧体界面处Nb’”，Ph’”，Ni‘”，Fe’“离于的扩散系数，其大小依次为 DFe＞DNb＞Dpb＞DN；： 研究了COF3＃叠层共烧体组成元素的化合价态，结果表明在JD材料与TY 材料共烧时无离子变价现象，各主要元素如 Ph、Nb、Ni和 Fe等均以常规价态存 在；通过对JD材料和TY材料的唯象动力学分析表明两种材料的晶粒生长机制 为扩散控制机制；探讨了界面处晶粒异常长大的机理，证实在叠层共烧体靠近界 面处介电材料晶粒异常长大是由于共烧过程中 re’”从铁氧体材料一侧扩散至介电 材料一侧并固溶于介电材料的钙钛矿晶格中所致。叠层共烧体中当保温时间超过 Zh后晶粒尺寸差别因子随保温时间的延长而减小是由于 Fe’”在 JD材料的钙钛矿 相晶格中固溶到一定量时趋于饱和，减缓了界面处晶粒生长速度所致。 采用电介质物理学等效电路分析研究了COF3＃叠层共烧体的介电频率响应， 计算了等效电路参数，用德拜弛豫理论解释介电频率响应，探讨了界面层对介电 性能的影响，并估算了界面层的等效电路参数和界面层的厚度。结果表明，叠层 共烧体的介电常数随频率的增加而减小，介电损耗随着频率的增?更多还原

【Abstract】 Recently,the surface mount technology (SMT) has been rapidly developed for miniaturization of electric devices such as multilayer ceramic capacitor (MLCC) and multilayer chip inductor (MLCI). Multilayer chip LC filter (MLLC),which is combined with several capacitors and inductors by the production process of multilayer chip components,is a type of advanced surface mount devices (SMD). Lead based relaxor ferroelectrics,and NiCuZn ferrite are promising materials for the multilayer chip LC filters. The key issue of manufacturing multilayer chip LC filters is cofiring the capacitors and inductors together at low temperature. In the present study,the multilayer components were prepared by cofiring Pb(Ni1/3Nb2/3)O3-PbTiO3 (abbreviated as PNN-PT) based ferroelectrics and NiCuZn ferrite. The cofiring properties and interfacial interactions such as chemical reaction,ionic interdiffusion between the constituents were investigated.Firstly,the rules of choosing dielectric material for Multilayer chip LC filter are proposed. According to the rules,0.8Pb(Ni1/3Nb2/3)O3-0.2PbTiO3 (0.8PNN-0.2PT) ceramic was chosen as the basis dielectric material. W03 and CuO were added into it to lower the sintering temperature. The phase structure and dielectric properties were investigated. The results show that CuO can not decrease the sintering temperature effectively as WO3 can do. The low-temperature-sintered PNN-PT-based ceramics with excellent dielectric properties are successfully prepared.Secondly,the multilayer components were prepared by cofiring PNN-PT-based ferroelectrics and (Ni0.5Cu0.4Zn0.1)Fe2O4 ferrite. The interaction,cofiring properties,camber development,and interface microstructure were investigated. The results show that there is no chemical reaction between the ferroelectrics and ferrite materials. The camber of the composites was observed at the cofiring temperature range from 800C to 950C. It shows that the grain of ferroelectrics adjacent to the interface is larger than that far from the interface. The difference factor dD is proposed to describe the microstructure difference between the interface and the inner parts. The difference factor decreases with increasing sintering temperature from 800 C to 900C.The camber development mechanism and the influence factors were researched by geometry analysis,viscous analysis and sintering kinetics analysis. The camber model was established and the equation for calculating curvature of camber was proposed. The influence factors for camber involve the original size of composite,the sintering properties and the shrinkage mismatch between the two materials. The more the shrinkage mismatch is,the larger the curvature is. The calculated results are in agreement with the experimental results.Thirdly,the cofired materials were adjusted according to the analysis of camber mechanism. The densification kinetics of the new cofiring system was thoroughly investigated and the apparent activation energy of sintering was calculated. The results show that the sintering mechanism of PNN-PT-based low-temperature-sintered ceramics (JD) is controlled not only by grain lattice diffusion,but also by grain boundary diffusion. The sintering mechanism of (Ni0.8Cu0.12Zn0.12)Fe1.96O4 ferrite material (TY) is mainly controlled by grain boundary diffusion. The apparent activation energy of JD and TY materials are 162 - 174KJ/mol and 208 - 235 KJ/mol,respectively. After these researches,the equations for densification kinetics of JD and TY materials are established.The effect of sintering time on the phase structure and microstructure was also investigated. It reveals that the perovskite phase of JD material decreases with increasing sintering time. The sintering time has no effect on the phase structure of TY ferrite. The grain size of both JD ferroelectrics and TY ferrite increases with increasing sintering time. 2 hours is the best sintering time.The multilayer composites (COF3#) were prepared at 900 C by cofiring JD ferroelectrics and TY ferrite using tape casting processes. The micros更多还原