Engineering of microstructures of protonic ceramics by a novel rapid laser reactive sintering for ceramic energy conversion devices

The solid state reactive sintering (SSRS) characteristic with the assistance of sintering aids (e.g., NiO) has been proven to be an effective method for achieving high-quality proton conducting oxide electrolytes at relatively low sintering temperatures (e.g., <1400 °C). In this work, instead of performing a long-term (e.g., >10 h) SSRS in a conventional high-temperature furnace, a novel rapid laser heating process was used to perform SSRS, which was named as rapid laser reactive sintering (RLRS). This RLRS method was confirmed to be able to sinter protonic ceramics with well-engineered microstructures within a short time (e.g., <10 s). Using the proton conducting oxides of BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) and BaZr0.8Y0.2O3-δ (BZY20) as case study, the crack-free protonic ceramic parts of straight strips (~10 mm in length, ~1 mm in width, and 30-200 μm in thickness), spiral strips (~200 mm in length, ~1 mm in width, and 30-200 μm in thickness), and squared films (~4.5 mm in both length and width and 30-200 μm in thickness) were successfully fabricated by RLRS method. The sintered parts usually showed fully dense large-grained and highly porous regions, which can potentially serve as electrolytes and electrode scaffolds for single cells or half-cells. The X-ray diffraction results indicated that the pure perovskite structures were obtained for both BCZYYb and BZY20 by RLRS from inexpensive carbonates and single metal oxides. The preliminary electrochemical impedance measurement for the dense strips after removal of porous regions by picosecond laser machining showed a reasonable in-plane protonic conductivities. This new RLRS method demonstrated the feasibility and promise of the rapid additive manufacturing of hierarchical ceramic energy conversion devices.