High piezoelectric and ferroelectric properties have been found in Mn-doped ${\text{Na}}_{0.5}{\text{Bi}}_{0.5}{\text{TiO}}_3–{\text{BaTiO}}_3$ single crystals, which were grown by a top-seeded solution method. The electrical resistivity, dielectric constant, and ferroelectric and piezoelectric properties were all found to be notably enhanced by Mn. The piezoelectric constant $d_{33}$ and electromechanical coupling coefficients $k_t$ and $k_{31}$ were found to be as high as 483 pC/N, 0.56, and 0.40, respectively. These values are much higher than those previously reported for Pb-free piezoelectric crystals, demonstrating the real potential for alternative lead-free systems for sensor and piezoelectric applications.

High-performance (Na_0.5Bi_0.5)TiO₃ (NBT) lead-free incipient ceramics are promising piezoactuator materials, but high driving fields to deliver the large strain limits their practical applications. Herein, we report a giant piezoelectric strain (d₃₃*) of 810 pm V⁻¹ at a low driving field of 4 kV mm⁻¹ in a novel ternary (0.94 − x)(Na_0.5Bi_0.5)TiO₃–0.06Ba(Zr_0.05Ti_0.95)O₃−x(Sr_0.8Bi_0.1□_0.1)TiO_2.95 solid solution with x = 0.05 (SBT5). The field of SBT5 critical composition is notably reduced compared with other NBT-based ceramics, while its strain properties are maintained at a high level along with an excellent thermal stability. The dopant induces a randomly distributed local polarization field, which breaks the symmetry of Landau potential curves, boosts the ferroelectric instability and favors a more disordered relaxor structure. The giant strain in the critical composition SBT5 is due to a field-induced reversible relaxor-ferroelectric phase transformation, while the reduced driving field results from two synergistic effects: remanent quasi-ferroelectric order as the seed for the growth of polar domains helps the system skip the nucleation process; the local defects further facilitate the growth of ferroelectric domains. The composition, temperature and electric-field dependence of structural evolutions were systematically elucidated from the micro- and macroscopic view. This study opens up a feasible and effective way for achieving giant electrostrain in lead-free actuator materials.

Magnetoelectric (ME) laminate composite consisting of optimal crystal cut thickness-polarized piezoelectric $0.7\mathrm{Pb}\left({\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}\right){\mathrm{O}}_3–0.3\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_3$ (PMN-PT) single crystal and the length-magnetized magnetostrictive ${\mathrm{Tb}}_{0.3}{\mathrm{Dy}}_{0.7}{\mathrm{Fe}}_{1.92}$ (Terfenol-D) alloy has been fabricated. The cut optimization of PMN-PT crystal greatly enhances the longitudinally magnetized-transversely polarized $\left(L\text{‐}T\right)$ mode ME effect, which has a superior ME voltage coefficient ${\alpha }_E$ of $\sim 3.02\mathrm{V}∕\mathrm{cm}\mathrm{Oe}$ in low frequency band. Near the resonance frequency of $95\mathrm{kHz}$ , the coefficient dramatically increases and reaches the maximized value of $33.2\mathrm{V}∕\mathrm{cm}\mathrm{Oe}$ , which is almost two times larger than the previously reported ⟨001⟩-oriented PMN-PT crystal based $L\text{‐}T$ mode laminate composite.