Near-ideal electromechanical coupling in textured piezoelectric ceramics

"k" is the electromechanical coupling factor, and determines the efficiency of conversion between electrical and mechanical energy or vice-versa in piezoelectric materials. Here, Yan et al. present an optimization strategy for "k" via texturing and covalency tuning that results in "k" values comparable to that of single crystals. Electromechanical coupling factor, k, of piezoelectric materials determines the conversion efficiency of mechanical to electrical energy or electrical to mechanical energy. Here, we provide an fundamental approach to design piezoelectric materials that provide near-ideal magnitude of k, via exploiting the electrocrystalline anisotropy through fabrication of grain-oriented or textured ceramics. Coupled phase field simulation and experimental investigation on textured Pb(Mg1/3Nb2/3)O-3-Pb(Zr,Ti)O-3 ceramics illustrate that k can reach same magnitude as that for a single crystal, far beyond the average value of traditional ceramics. To provide atomistic-scale understanding of our approach, we employ a theoretical model to determine the physical origin of k in perovskite ferroelectrics and find that strong covalent bonding between B-site cation and oxygen via d-p hybridization contributes most towards the magnitude of k. This demonstration of near-ideal k value in textured ceramics will have tremendous impact on design of ultra-wide bandwidth, high efficiency, high power density, and high stability piezoelectric devices.