Heterostrain-enabled ultrahigh electrostrain in lead-free piezoelectric

Abstract

Piezoelectric materials provide high strain and large driving forces in actuators and can transform electrical energy into mechanical energy. Although they were discovered over 100 years ago, scientists are still searching for alternative lead-free piezoelectrics to reduce their environmental impact. Developing high-strain piezoelectric materials has been a long-term challenge, particularly challenging for the design of high-strain polycrystalline piezoelectrics containing no toxic lead element. In this work, we report one strategy to enhance the electrostrain via designing “heterostrain” through atomic-scale defect engineering and mesoscale domain engineering. We achieve an ultrahigh electrostrain of 2.3% at high temperature (220 °C) in lead-free polycrystalline ceramics, higher than all state-of-the-art piezoelectric materials, including lead-free and lead-based ceramics and single crystals. We demonstrate practical solutions for achieving high electrostrain in low-cost environmentally piezoelectric for various applications.

Giant electric field–induced strain in lead-free piezoceramics

“…When an external electric field is applied, the defect dipoles drive stretching or contraction of the surrounding lattice and interact with the domain switching, leading to the asymmetric S-E curve, even under high electric field conditions. More recently, similar strain behavior has also been reported in NBT ceramics ( 29 ), in which ultrahigh strain is associated with switching between disordered and ordered polarization states, complex structure with multiphase coexistence, non-180° switching, and domain stabilization. The polarization in KNSN3 samples, however, can be almost reversed by the electric field (fig.…”

Achieving giant electrostrain of above 1% in (Bi,Na)TiO 3 -based lead-free piezoelectrics via introducing oxygen-defect composition

“…For example, electric field-induced rearrangement of oxygen vacancies resulted in extraordinarily high piezoelectricity in Gd-doped CeO 2 -x thin films (26). More recently, a similar strain behavior has been reported in BNT ceramics, where the A-site ion displacement and octahedral distortion induced by the oxygen vacancies and strong electric field are thought to be responsible for the huge strain (21). Introduction of defects into a lattice usually forms defect dipoles that can be oriented by aging (27,28).…”

“…The mesoscopic structural modifications such as designing core-shell structures or tailoring the domain structures by periodic orthogonal poling can boost the electrostrain via enhancing reversible non-180° domain switching ( 16 , 20 ). Of particular interest is that the BiFeO 3 -PbTiO 3 -LaFeO 3 (BF-PT-LF) lead-based system achieved a record value of 1.3% by synergistically improving the intrinsic and extrinsic contributions to electrostrain ( 15 ), which is a representative perovskite-based ceramic systems with a strain greater than 1% ( 21 , 22 ).…”

“…Materials that produce a strain in response to an applied electric field are critical for actuator usage (4,5). Considerable research efforts on perovskite ferroelectrics over the past decades have led to the discovery of many materials with excellent electrostrain properties (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Among these materials, lead-free Bi 0.5 Na 0.5 TiO 3 (BNT)-based ceramics have relatively large electric field-induced strains but with reported electrostrains being lower than 0.5% (4).…”

“…It is generally believed that the electrostrain in ferroelectrics is attributed to intrinsic piezoelectric effect (8,9), polarization rotation (10), field-induced phase transitions (11)(12)(13)(14)(15), domain switching (16)(17)(18)(19)(20), defect regulation (21,22), etc. Several approaches have been developed to achieve high electrostrains.…”