Preserving nickel electrode conductivity during sintering process using lithium carbonate coatings

The resistance of nickel particles can be decreased by five orders of magnitude when coated with lithium carbonate during sintering in an oxidative atmosphere. The resistance is within a range, in which use is suitable for electrodes in the electroceramic devices. The coated powders have the potential to replace the precious metals (e.g. Pt and Ag) in multilayer electroceramic devices. A systematic study of the influence of sintering atmosphere and temperature on the morphology of Li₂CO₃-coated Ni particles was investigated via TEM (transmission electron microscopy), SEM-FIB (scanning electron microscopy - focused ion beam) imaging, and TGA (thermogravimetric analysis). The results suggested that the Li₂CO₃decomposes and produces CO in the presence of residual carbon; CO, as a reducing agent, decreases the amount of NiO phases formed during sintering. At the same time, the NiO phase was doped with Li⁺, resulting in a decrease in its resistivity. The combination of these two processes decreased the resistance of the final Ni electrodes from 140 kΩ to 1 Ω. The effect and role of these two mechanisms were separated, and it is shown that both of them are equally useful in the preservation of electrical conductivity.