Highly HFOM three-dimensional anti-tetrachiral negative Poisson's ratio BaTiO3 ceramics prepared via vat photopolymerization

As lead-free piezoelectric ceramics with high electromechanical conversion performance, Barium Titanate (BaTiO₃) has been widely used in fields such as hydrophones and energy collection. Negative Poisson's ratio (NPR) structures can resist compression in the vertical direction when subjected to compressive force and exhibit an auxetic effect in the horizontal direction. This feature provides new degrees of freedom for material design, especially in high-performance application scenarios that require specific mechanical responses. In this paper, the optimal preparation process of BaTiO₃ ceramics was established by studying the influence of the mass ratio of submicron/micron BaTiO₃ particles on the rheological properties and curing properties of the slurry, as well as the mechanical and electrical properties of ceramics under different sintering processes. The prepared bulk BaTiO₃ had a relative density of 97.9 %, a compressive strength of 300.2 MPa, a piezoelectric strain coefficient d₃₃ of 275 pC/N, and a hydrostatic figure of merit (HFOM) of 0.0812 × 10⁻¹² Pa⁻¹. Two types of BaTiO₃ ceramics with Positive Poisson's ratio (PPR) structure, Body-centered Cubic (BCC) and Simple Grid Cubic (SGC) were designed and prepared, and their performance was compared with that of BaTiO₃ ceramics with NPR structure at the same porosity, proving the performance improvement effect of NPR structure on BaTiO₃ ceramics. In this paper, we started from the two aspects of process parameter optimization and NPR structural configuration parameter design and used vat photopolymerization (VPP) 3D printing technology to prepare Three-dimensional NPR structural BaTiO₃ ceramics with high hydrostatic piezoelectric strain coefficient d_h (520 pC/N) and HFOM (88.26 × 10⁻¹² Pa⁻¹), 1085 times higher than that of the bulk BaTiO₃. The results of this work guided the design and preparation of piezoelectric ceramics and also showed the great potential of VPP 3D printing technology in developing structural piezoelectric ceramics with high electromechanical response.