Highly tailorable electromechanical properties of auxetic piezoelectric ceramics with ultra‐low porosity

Abstract Conventional porous piezoelectric ceramics can possess superior figures of merit only at very high values of porosity, leading to bad fragileness, small stiffness, low toughness, and the difficulty of polarization. To this end, this study for the first time shows that it is possible that the piezoelectric ceramic with ultra‐low porosity is capable of superior figures of merit based on the concept of auxetic piezoelectric ceramics. Owing to the ultra‐low porosity and auxetic effect, the auxetic piezoelectric ceramic shall also possess larger stiffness, higher toughness, and is more easily polarized. First, the auxetic piezoelectric ceramic with ultra‐low porosity is proposed to achieve highly tunable electromechanical properties on the basis of the rotating square mechanism. Then, using a multiscale finite element method, the effects of geometric architecture and polarization directions on the electromechanical properties including Poisson's ratios, elastic coefficients, piezoelectric stress coefficients, dielectric coefficients, and figures of merit in the auxetic piezoelectric ceramics are investigated in detail. Furthermore, the stress fields in conventional and proposed porous piezoelectric ceramics subjected to mechanical and electrical loads are compared and discussed. Finally, it can be concluded that the auxetic piezoelectric ceramic exhibits (a) giant negative Poisson's ratios (smaller than ), (b) negative elastic coefficients, (c) more extensible, higher piezoelectric sensitivity, lower acoustic impedance, stronger crack resistance than conventional porous piezoelectric ceramics with the same porosity, and (d) larger stiffness than conventional porous piezoelectric ceramics with similar figures of merit.