Center for Dielectrics and Piezoelectrics, Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
ACS Appl Mater Interfaces. 2016 Nov 16;8(45):31449-31459. doi: 10.1021/acsami.6b11039. Epub 2016 Nov 1.
Both LiCO-coated nickel particles and fast firing technique were utilized in the manufacturing of MLCCs. They preserved the conductivity of Ni electrodes and provided the possibility of sintering the devices in oxidizing atmospheres. By using our method, the partial pressure of oxygen increased from 10 atm in conventional methods to 10 atm. The oxidizing atmosphere reduced the oxygen vacancy concentration as illustrated by the color change of the samples, and the results of EELS (electron energy loss spectroscopy). A systematic test with variable parameters, LiCO coating, the sintering schedule, and the oxygen flow during sintering were executed, and the dissipation factor and the capacitance of the MLCCs were documented. Three type of MLCCs were studied: Conventional (fired with the conventional technique), Uncoated (fast fired with uncoated Ni particles), and Coated (fast fired with the coated Ni particles). The maximum oxygen activity during sintering (i.e., pO = 1.2 × 10 atm) was obtained for coated samples, and due to the minimum V concentration, their dissipation factor decreased up to 60% relative to the Conventional ones. In addition, the impedance spectroscopy, together with the map of Li ion distribution, suggested that Li ions accumulated around the electrode-dielectric interface and amplified the activation energy at these interfaces. This eventually caused the coated MLCCs to show higher capacitance than their uncoated counterparts. As a conclusion, it is shown that the manufacturing process described in this paper can provide a better MLCC with higher capacitance, and lower dissipation factor and leakage current.
在 MLCC 的制造过程中，使用了 LiCO 涂层的镍颗粒和快速烧结技术。它们保留了 Ni 电极的导电性，并为在氧化气氛中烧结器件提供了可能性。通过使用我们的方法，氧气分压从传统方法中的 10 大气压增加到了 10 大气压。氧化气氛降低了氧空位浓度，正如样品的颜色变化和 EELS（电子能量损失光谱）的结果所示。通过执行具有可变参数的系统测试，LiCO 涂层、烧结计划以及烧结过程中的氧气流量，记录了 MLCC 的损耗因子和电容。研究了三种类型的 MLCC：传统型（用传统技术烧结）、无涂层型（用未涂层的 Ni 颗粒快速烧结）和涂层型（用涂层的 Ni 颗粒快速烧结）。涂层样品在烧结过程中获得了最大的氧活度（即 pO = 1.2 × 10 atm），由于 V 浓度最低，它们的损耗因子相对于传统型降低了高达 60%。此外，阻抗谱以及 Li 离子分布图表明，Li 离子在电极-电介质界面周围积累，并放大了这些界面处的激活能。这最终导致涂层 MLCC 的电容比无涂层的 MLCC 更高。总之，本文所述的制造工艺可以提供具有更高电容、更低损耗因子和漏电流的更好的 MLCC。
