Commercial lead-based piezoelectric materials raised worldwide environmental concerns in the past decade. Bi 0.5 Na 0.5 TiO 3 -based solid solution is among the most promising lead-free piezoelectric candidates; however, depolarization of these solid solutions is a longstanding obstacle for their practical applications. Here we use a strategy to defer the thermal depolarization, even render depolarization-free Bi 0.5 Na 0.5 TiO 3 -based 0-3-type composites. This is achieved by introducing semiconducting ZnO particles into the relaxor ferroelectric 0.94Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 matrix. The depolarization temperature increases with increasing ZnO concentration until depolarization disappears at 30 mol% ZnO. The semiconducting nature of ZnO provides charges to partially compensate the ferroelectric depolarization field. These results not only pave the way for applications of Bi 0.5 Na 0.5 TiO 3 -based piezoceramics, but also have great impact on the understanding of the mechanism of depolarization so as to provide a new design to optimize the performance of lead-free piezoelectrics.

Both low strain hysteresis and high piezoelectric performance are required for practical applications in precisely controlled piezoelectric devices and systems. Unfortunately, enhanced piezoelectric properties were usually obtained with the presence of a large strain hysteresis in BaTiO (BT)-based piezoceramics. In this work, we propose to integrate crystallographic texturing and domain engineering strategies into BT-based ceramics to resolve this challenge. [001] grain-oriented (BaCa)(TiZr)O (BCTZ) ceramics with a texture degree as high as 98.6% were synthesized by templated grain growth. A very high piezoelectric coefficient (d) of 755 pC/N, and an extremely large piezoelectric strain coefficient (d* = 2027 pm/V) along with an ultralow strain hysteresis (H) of 4.1% were simultaneously achieved in BT-based systems for the first time, which are among the best values ever reported on both lead-free and lead-based piezoceramics. The exceptionally high piezoelectric response is mainly from the reversible contribution, and can be ascribed to the piezoelectric anisotropy, the favorable domain configuration, and the formation of smaller sized domains in the BCTZ textured ceramics. This study paves a new pathway to develop lead-free piezoelectrics with both low strain hysteresis and high piezoelectric coefficient. More importantly, it represents a very exciting discovery with potential application of BT-based ceramics in high-precision piezoelectric actuators.

Lead-free single crystal, (K, Na, Li)(Nb, Ta)O3:Mn, was successfully grown using top-seeded solution growth method. Complete matrix of dielectric, piezoelectric and elastic constants for [001]C poled single crystal was determined. The piezoelectric coefficient d33 measured by the resonance method was 545 pC/N, which is almost three times that of its ceramic counterpart. The values measured by the Berlincourt meter ( d33∗=6300.16667empC/normalN) and strain-field curve ( d33∗∗=8700.16667empm/normalV) were even higher. The differences were assumed to relate with the different extrinsic contributions of domain wall vibration and domain wall translation during the measurements by different approaches, where the intrinsic contribution (on the order of 539 pm/V) was supposed to be the same. The crystal has ultrahigh electromechanical coupling factor (k33 ~ 95%) and high ultrasound velocity, which make it promising for high frequency medical transducer applications.

1Àx)(Bi 0.5 Na 0.5 )TiO 3 -xBa(Zr 0.055 Ti 0.945 )O 3 (0 x 0.12) lead-free ceramics have been prepared and the morphotropic phase boundary (MPB) is confirmed to be x ¼ 0.06-0.09. The MPB composition x ¼ 0.07 shows enhanced pyroelectric properties from room temperature (RT) to the depolarization temperature T d (87 C), with the pyroelectric coefficient p ¼ 0.057 lC/cm 2 C and the figures of merit F i ¼ 203 pm/V, F v ¼ 0.022 m 2 /C, and F d ¼ 10.5 lPa À1/2 at RT and the highest pyroelectric coefficient of 2.21 lC/cm 2 C near T d . These values are superior to other lead-based/lead-free pyroelectric ceramics. Enhanced pyroelectric properties can be explained by the effects of MPB and ferroelectric-antiferroelectric phase transition. V C 2013 AIP Publishing LLC.