BaTiO3基 X9R 型多层陶瓷电容器介电材料的研究

STUDY OF DIELECTRIC MATERIALS FOR BaTiO3 BASED MLCC REQUIRED BY X9R

郭瑞

11849274

硕士

材料工程领域工程

杨改英

2020-05-28

2020-07-20

哈尔滨工业大学

深圳

多层陶瓷电容器，特别是 Ni-BaTiO3 贱金属多层陶瓷电容器，具有优越的性价比，已经广泛应用于各类微电子器件中。随着这类器件应用领域的进一步拓展，对其性能也提出了更高的要求。某些国防应用以及汽车电子领域的应用对电容器的服役温度还有更高的要求，使得高端 MLCC 器件的研发朝着超薄层、高容量化及高温稳定化的趋势进行。为此，本研究采用 BaTiO3 粉体为基体材料，通过固相法，成功制备了使用上限温度为 200℃的 MLCC 介电材料。本文采用固相法制备了纳米级具有高居里温度和复合钙钛矿结构的钛酸铋钠粉体，合成了具有相对高的居里温度点的 xBT-(1-x)BNT 铁电陶瓷。研究了BNT 添加量对 BT-BNT 固溶体居里温度点的影响，其中 0.9BT-0.1BNT 居里温度为 190℃。利用 SEM、TEM、XRD 等表征技术研究了 BT-BNT 陶瓷的微观结构，研究表明 BT-BNT 固溶体陶瓷在室温下为四方钙钛矿结构，并且具有铁电畴结构。通过固相法掺杂 Nb2O5 对 0.9BT-0.1BNT 固溶体陶瓷进行掺杂改性研究，改善了 BT-BNT 陶瓷的容温稳定性，其中 Nb2O5 掺杂量为 2.0 mol%的陶瓷满足EIA X9R 型标准。纳米尺度的微区结构观察和微区化学组分分析（TEM/STEM/EDS）揭示了 Nb 在陶瓷晶粒内的分布特征，即 Nb 仅扩散到 BT BNT 晶粒表层而没有到达晶粒中心，这是“芯-壳”结构形成的主要原因。在此基础上，还进一步研究了 MgO、MgCO3、Dy2O3 以及 Ho2O3 等掺杂剂对 0.9BT-0.1BNT-Nb 基陶瓷的介电性能和微观结构的影响。研究表明 MgO 的掺杂会促进 Nb 在陶瓷晶粒内部的扩散，破坏了“芯-壳”结构，陶瓷不满足 EIA X9R 型标准。而 0.9BT-0.1BNT-Nb 基陶瓷在掺杂了 MgCO3、Dy2O3 以及 Ho2O3后，陶瓷晶粒具有“芯-壳”结构，容温变化率依然满足 EIA X9R 型标准。

Based on desirable performance-cost behavior, multilayer ceramic capacitors, especially Ni-BaTiO3 base metal multilayer ceramic capacitors (BME-MLCC), have been widely used in various microelectronic devices. With the application of this kind of devices in more and more fields, the devices with even better electrical performances are required. Applications, such as certain defense and automotive electronics, require highly the capacitors that could be used at relatively higher temperatures, leading to the development of MLCC devices with ultra-thin layers while higher capacitance and better stability in wider temperature range. In this work, the dielectric that maintains reasonable capacitance stability up to 200℃ was successfully prepared by solid phase method using BaTiO3 powder as matrix material.First, nano-scale bismuth titanate sodium powders with high Curie temperature and composite perovskite structure were prepared by solid-state method, then xBT-(1-x)BNT ferroelectric ceramics with relatively high Curie temperature were successfully synthesized. A series of studies on the effect of BNT addition on the Curie temperature of xBT(1-x)BNT solid solution was carried out. It is found that the sample of 0.9BT-0.1BNT shows Curie temperature of 190℃. Microstructure of BT BNT ceramics was characterized by using SEM, TEM, and XRD, respectively. It has been revealed that xBT(1-x)BNT is solid solution of tetragonal perovskite structure with ferroelectric domain at room temperature.The capacitance stability of BT-BNT ceramics in the temperature range from -55°C to 200°C has been significantly improved by adding 2.0 mol% Nb2O5 into 0.9 BT-0.1BNT solid solution, which meets the requirement for EIA X9R. mixrostructure and microchemistry investigation at nano-scale by TEM/STEM/EDS revealed that the dopant Nb distributs inhomegenesly within the ceramic grains. Nb is mainly located in the area next to grain boundary, and it is most likely free of Nb inside ceramic grain. Such Nb distribution in BTBNT grain is responsible for the formation of "core-shell" structure. In addition, the influence of dopants, such as MgO, MgCO3, Dy2O3, and Ho2O3, on the dielectric properties and microstructure of 0.9BT-0.1BNT-Nb based ceramics was also investigated. It has been showed that the MgO doping accelerates the Nb diffusion inside the whole grains. Most likely Nb is present whole grain, resulted in the disappearance of "core-shell" structure. The dielectric with MgO dopant won’t meet the EIA X9R requirements. However, "core-shell" structure is well maintained in 0.9BT-0.1BNT-Nb based ceramics with dopants, such as MgCO3, Dy2O3, and Ho2O3. The capacitance-temperture stability is well meets the EIA X9R requirements.

多层陶瓷电容器 居里温度 “芯—壳”结构 介电材料

multilayer ceramic capacitor curie temperature "core-shell" structure dielectrics material

中文

联合培养

南方科技大学

郭瑞. BaTiO3基 X9R 型多层陶瓷电容器介电材料的研究[D]. 深圳. 哈尔滨工业大学,2020.