Design of superior electrostriction in BaTiO_(3) -based lead-free relaxors via the formation of polarization nanoclusters

Electrostrictive materials have wide applications in modern high-precision electronic devices.Driven by growing environmental concerns,there is demand for lead-free materials with superior electrostriction behaviors.In this study,we demonstrate a record-high electrostrictive coefficient of~0.0712 m^(4) C^(-2) in perovskite ferroelectric ceramics,along with hysteresis-free strain as well as excellent frequency and thermal stabilities,in lead-free BaTiO_(3)-based ceramics through a polarization nanocluster design.By appro-priately introducing Li+and Bi^(3+)into the BaTiO 3 lattice matrix,the long-range ferroelectric ordering can be broken,and polarization nanoclusters can be formed,resulting in a relaxor state with concurrently suppressed polariza-tion and maintained electro-strain.A three-dimensional atomic model constructed using advanced neutron total-scattering data combined with the reverse Monte Carlo method indicates the existence of Bi and Li segregations at the subnanometer scale,which confirms the prediction made by density functional theory calculations.Such a short-range chemical order destroys the long-range ferroelectric order of the off-centered Ti polar displacements and leads to the embedding of Li+/Bi ^(3+)-rich polar nanoregions in the Ba^(2+)-rich polarization disorder matrix.Further,a completely reversible electric-field-induced lattice strain is observed,giving rise to pure electrostriction without hysteresis behavior.This work provides a novel strategy for developing lead-free relaxor ferroelectrics with high electrostriction performance.

Ferroelectric-to-relaxor transition and ultrahigh electrostrictive effect in Sm^(3+)-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)ferroelectrics ceramics

Rare-earth Sm^(3+)-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.25PbTiO_(3)(PMN-0.25PT)ferroelectric ceramics with doping amounts between 0%-3%were developed via a conventional solid-state method.The doping effect of Sm^(3+)ions on the PMN-0.25PT matrix was systematically investigated on the basis of the phase structure,temperature-dependent dielectric,ferroelectric,and electrotechnical properties.Due to the disruption of long-range ferroelectric order,the addition of Sm^(3+)ions effectively lowers the Tm(temperature corresponding to maximum permittivity)of the samples,leading to enhanced relaxor ferroelectric(RFE)characteristic and superior electric field-induced strain(electrostrain)properties at room temperature.Intriguingly,a considerable large-signal equivalent piezoelectric coefficient d∗_(33)of 2376 pm/V and a very small hysteresis were attained in the PMN-0.25PT component doped with 2.5 mol.%Sm^(3+).The findings of piezoelectric force microscopy indicate that the addition of Sm^(3+)increases the local structural heterogeneity of the PMN-0.25PT matrix and that the enhanced electromechanical performance is due to the dynamic behavior of polar nanoregions.Importantly,strong temperature-dependent electrostrain and electrostrictive coefficient Q33 are observed in the critical region around Tm in all Sm^(3+)-modified PMN-0.25PT ceramic samples studied.This work elucidates the phase transition behavior of Sm^(3+)-doped PMN-0.25PT and reveals a critical region where electrostrictive properties can be greatly improved due to a strong temperature-dependent characteristic.

Polyurethane-based Actuators with Various Polyols

This study dealt with the electrostrictive responses of polyurethane （PU） actuators with different microphase separation structure, which was a promising candidate for a material used in polymer actuators. In order to construct PUs with different higher-order structure, PUs with various types of polyol were synthesized： poly（neopentyl glycol adipate） （PNAD）, poly（tetramethylene glycol） （PTMG）, and poly（dimethyl siloxnae） （PDMS）. Synthesized PU was characterized by Fourier transform-infrared （FT-IR） spectroscopy and gel per- meation chromatography （GPC）. Thermal analysis and mechanical properties of PU films were carried out with differential scanning calorimetry （DSC） and UTM （universal testing machine）, respectively. And PU actuator was formed in a type of monomorph, which was made by carbon black electrodes on the both surfaces of PU film by spin coating method. Actuation behavior was mainly influenced on microphase separation struc- ture and mechanical property of PU. In result, PU actuator with PNAD, polyester urethane, had the largest field-induced displacement.