1 research outputs found
Redesigning Multilayer Ceramic Capacitors by Preservation of Electrode Conductivity and Localized Doping
Both Li<sub>2</sub>CO<sub>3</sub>-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<sup>–10</sup> atm in conventional
methods to 10<sup>–4</sup> 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, Li<sub>2</sub>CO<sub>3</sub> 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<sub>2</sub> = 1.2 × 10<sup>–4</sup> atm) was obtained for
coated samples, and due to the minimum <i>V</i><sub>O</sub><sup>••</sup> 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