Lead-Free Textured Ceramics with Ultrahigh Piezoelectric Properties by Synergistic Design.

Lead-free ceramics with superior piezoelectric performance are highly desirable in various electromechanical applications. Unfortunately, it is still challenging to achieve significantly enhanced piezoelectricity without sacrificing the Curie temperature (Tc) in current BaTiO3-based ceramics. To address this issue, a synergistic design strategy of integrating crystallographic texture, multiphase coexistence, and doping engineering is proposed here. Highly [001]c-textured (Ba0.95Ca0.05)(Ti0.92Zr0.06Sn0.02)O3 ceramics are synthesized through Li-related liquid-phase-assisted templated grain growth, with improved grain orientation quality (f of ∼96% and r of ∼0.16) achieved at substantially reduced texture temperatures. Encouragingly, ultrahigh comprehensive piezoelectric properties, i.e., piezoelectric coefficient d33 of ∼820 pC N-1, electrostrain Smax/Emax of ∼2040 pm V-1, and figure of merit d33 × g33 of ∼23.5 × 10-12 m2 N-1, are simultaneously obtained without sacrificing Tc, which are also about 2.3, 2.4, and 4.3 times as high as those of non-textured counterpart, respectively. On the basis of the experiments and theoretical modeling, the outstanding piezoelectric performance is attributed to more effective exploration of property anisotropy and easier polarization rotation/extension, owing to improved grain orientation quality, dissolution of templates into oriented grains, coexisting R + O + T phases, and domain miniaturization. This work provides important guidelines for developing novel ceramics with outstanding piezoelectric properties and can largely expand application fields of textured BaTiO3-based ceramics into high-performance and multilayer electronic devices.

Lead zirconate titanate ceramics with aligned crystallite grains.

The piezoelectric properties of lead zirconate titanate [Pb(Zr,Ti)O3 or PZT] ceramics could be enhanced by fabricating textured ceramics that would align the crystal grains along specific orientations. We present a seed-passivated texturing process to fabricate textured PZT ceramics by using newly developed Ba(Zr,Ti)O3 microplatelet templates. This process not only ensures the template-induced grain growth in titanium-rich PZT layers but also facilitates desired composition through interlayer diffusion of zirconium and titanium. We successfully prepared textured PZT ceramics with outstanding properties, including Curie temperatures of 360°C, piezoelectric coefficients d33 of 760 picocoulombs per newton and g33 of 100 millivolt meters per newton, and electromechanical couplings k33 of 0.85. This study addresses the challenge of fabricating textured rhombohedral PZT ceramics by suppressing the otherwise severe chemical reaction between PZT powder and titanate templates.

Compositionally Graded KNN-Based Multilayer Composite with Excellent Piezoelectric Temperature Stability.

The inherent disadvantage of lead-free potassium sodium niobate (KNN)-based ceramics is the severe temperature instability of piezoelectric charge coefficient (d33 ) caused by the polymorphic phase boundary. Herein, a new concept of structural gradient is proposed by designing compositionally graded multilayer composites with multiple successive phase transitions, to solve the challenge of the inferior temperature stability. The structural gradient ceramics exhibit a superior temperature reliability (d33 remains almost unchanged in the temperature range of 25-100 °C), far outperforming the previously reported KNN counterparts with d33 variation above 27% over the same temperature range. The synergistic contribution of the continuous phase transition, the strain gradient, and the complementary effect of each constituent layer leads to the excellent temperature stability, which is also confirmed by phase-field simulation. These findings are expected to provide a new paradigm for functional material design with outstanding temperature stability.