Novel 3D printed BaTiO3-based ceramics with high PTC effect via vat photopolymerization and vacuum infiltration

Structural modification is a feasible and effective method to improve the heating efficiency and uniformity of BaTiO₃-based ceramics with positive temperature coefficient (PTC) of resistance. However, modifying three-dimensional (3D) structures by traditional manufacturing methods is very challenging due to the inhomogeneous mixing of raw materials and high mold dependency. Additionally, the realization of complex structures using emerging vat photopolymerization (VPP) technology is limited by the poor curing properties of leaded PTC ceramic slurry. Herein, this study presents an innovative approach of combining VPP technology with vacuum infiltration (VI) process for fabricating high-performance PTC ceramics. Notably, the introduction of soluble starch significantly enhances the curing depth and printability of PTC ceramic slurry. Meanwhile, silica nanoparticles in silica sols are infiltrated into 3D printed green bodies to improve the electrical properties of PTC ceramics. At optimal soluble starch content and silica concentration, a lower room temperature resistivity (ρ=207 Ω·cm) and a higher temperature coefficient of resistance (α_0–15=25.14 %/℃) are obtained in printed PTC ceramics compared to dry pressed PTC ceramics (ρ=301 Ω·cm, α_0–15=19.32 %/℃). Therefore, this work provides a novel technological strategy for fabricating high-performance PTC ceramics with desirable structures and can promote the wide application of PTC heating elements.