Picosecond Laser Cutting-Assisted Rapid Laser Reactive Sintering for the Fabrication of Crack-Free Protonic Ceramic Electrochemical Cells

Nowadays, greenhouse gas emissions have become a more severe problem. Renewable energy sources are crucial to solve this problem. Protonic ceramic fuel cells (PCFCs) have been considered ideal for energy conversion and storage applications. Compared to oxide-ion, proton, as the charge carrier, has a much lower transport activation energy. This property leads to the wide application of protonic ceramics in intermediate-temperature electrochemical devices [1]. However, the refractory property of typical protonic ceramics makes the conventional furnace sintering methods for PCFCs ineffective and time-consuming. The rapid laser reactive sintering (RLRS), with the assistance of sintering aids, has shown its ability to sinter protonic ceramics in a short time (< 10 s) from cost-effective raw materials of oxides and carbonates. We have successfully demonstrated the feasibility of preparing crack-free BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3-δ (BCZYYb) electrolyte samples by RLRS [2]. However, it is not easy to achieve crack-free samples with a large area. Therefore, eliminating the cracks during sintering is key to sinter large area samples.

In the process of RLRS, the protonic ceramic experiences significant thermal stress. The cracks introduced by thermal stress originated from both sides of the straight stripe-shaped samples and propagated into the center area. In this work, we fabricated PCFC half cells using the RLRS method. In the half cell, we chose the 40wt% BCZYYb+60wt% NiO and BCZYYb as anode and electrolyte, respectively. The anode was 3D printed with 80mm in length, 15mm in width, and 200-300μm in thickness. The electrolyte was spray-coated on the anode surface. 1.0wt% of NiO added to the electrolyte served as the sintering aid. As mentioned before, during RLRS, the cracks originate from both sides of the samples. Because of the contact angle of the slurry on the substrate, both sides of the rectangular half cells have thickness variance, and this kind of inconsistency caused stress concentration. We utilized a picosecond laser to cut both sides of the samples. Besides, the thermal effect of picosecond laser can sinter a small area to provide compressive stress to the bulk of the sample due to sintering shrinkage. The cut samples with a reduced width of 11mm were then sintered using CO₂ laser in a scanning manner. A sample with a length of 80mm and a width of 11mm was prepared successfully. The combination of picosecond laser cutting and RLRS enabled us to manufacture large area crack-free co-sintered BCZYYB half cells quickly.

Keywords: 3D printing, Laser sintering, Reactive sintering, Picosecond laser, Protonic ceramic fuel cell.

References

1. Mu, S., Zhao, Z., Huang, H., Lei, J., Peng, F., Xiao, H., & Brinkman, K. S. (2020). Advanced Manufacturing of Intermediate-Temperature Protonic Ceramic Electrochemical Cells. The Electrochemical Society Interface, 29(4), 67.

2. Mu, S., Zhao, Z., Lei, J., Hong, Y., Hong, T., Jiang, D., ... & Tong, J. (2018). Engineering of microstructures of protonic ceramics by a novel rapid laser reactive sintering for ceramic energy conversion devices. Solid State Ionics, 320, 369.