Ferroelectric materials find extensive applications in brake systems due to their capability to convert electrical energy into mechanical energy.Recent research has focused on lead-free materials for their environment...Ferroelectric materials find extensive applications in brake systems due to their capability to convert electrical energy into mechanical energy.Recent research has focused on lead-free materials for their environmentally friendly characteristics.However,they exhibit several challenges such as significant negative strain,limited strain values,and large driving field.In this work,novel preparation techniques(electrospinning)were utilized for BaTiO_(3)to introduce oxygen vacancies and barium defects,facilitating the creation of oriented defect dipoles coupled with an intrinsic electric field(Ei)after poling and aging.Due to the existence of Ei,two minimum points in the strain hysteresis loop were shifted to the same quadrant in the Strain-Electric field space.Thus,when applying an electric field along the Ei direction,negative strain is eliminated.Additionally,the actual electric field is the sum of the applied electric field and Ei,thereby reducing the required driving field of the piezoelectric.The stretching of defect dipoles under the electric field further amplified the total strain.Through the proposed mechanisms,this work achieved a substantial unipolar electrostrain of 1.04%under a relatively low electric field(30 kV/cm)in BaTiO_(3).This work successfully addressed the challenges of high-driving electric fields,limited strain values,and negative strain,providing a comprehensive approach for improving field-induced strain performance through point defect engineering in ferroelectric materials.展开更多
The ferroelectric superlattices have been widely studied due to their distinguished electromechanical coupling properties.Under different biaxial mismatch strains,ferroelectric superlattices exhibit different domain s...The ferroelectric superlattices have been widely studied due to their distinguished electromechanical coupling properties.Under different biaxial mismatch strains,ferroelectric superlattices exhibit different domain structures and electromechanical coupling properties.A three-dimensional phase field model is employed to investigate the detailed domain evolution and electromechanical properties of the PbTiO_(3)/SrTiO_(3)(PTO/STO)superlattices with different biaxial mismatch strains.The phase field simulations show that the ferroelectric superlattice exhibits large electrostrain in the stacking direction when an external field is applied.Under a large compressive mismatch strain,vortex domains appear in ferroelectric layers with the thickness of 4 nm.The vortex domains become stable cdomain under a large external electric field,which remains when the electric field is removed.When the initial compressive mismatch strain decreases gradually,the waved or a1/a2 domains replaces the initial vortex domains in the absence of electric field.The fully polarized c-domain by a large electric field switches to diagonal direction domain or a/c domain when the electric field is small.Furthermore,when a biaxial tensile strain is applied to the superlattice,ferroelectric domains switch back to the initial a1/a2 twin-like domain structure,resulting in the recoverable and large electrostrain.This provides an effective way to obtain the large and recoverable electrostrain for the engineering application.展开更多
The development of multifunctional materials with optical and electrical properties has become a research hotspot in recent years.In this work,multifunctional 0.935(Bi_(0:5)Na_(0:5))TiO_(3)–0.065BaTiO_(3)(BNT–BT)-ba...The development of multifunctional materials with optical and electrical properties has become a research hotspot in recent years.In this work,multifunctional 0.935(Bi_(0:5)Na_(0:5))TiO_(3)–0.065BaTiO_(3)(BNT–BT)-based ferroelectric ceramics doped with small amounts of CaMAlO_(4)(M=Dy,Ho)were prepared,and the effect of CaMAlO_(4)on the electrostrain and photoluminescence properties of the ceramics was studied.The results showed that the CaMAlO_(4)addition weakened the ferroelectric properties of the BNT–BT matrix,and promoted the improvement of the electrostrain performance.For samples doped with 1.5 mol%CaMAlO_(4),the unipolar strain Suni reached the largest values,which were 0.33%(M=Dy)and 0.38%(M=Ho)under an electric field of 70 kV/cm,corresponding to a large signal d^(*)_(33)(Smax=Emax)of 471 pm/V(M=Dy)and 543 pm/V(M=Ho),respectively.In addition,due to the existing Dy^(3+)and Ho^(3+)luminescent ions,the modified samples exhibited excellent photoluminescence performance,which exhibited bright yellow emission(M=Dy)and green emission eM=HoT under the blue excitation.Due to their multifunctional features,these materials have potential applications as“on-off”actuators,optical-electro integration and coupling devices.展开更多
Over the past two decades,(K_(0.5)Na_(0.5))NbO_(3)(KNN)-based lead-free piezoelectric ceramics have made significant progress.However,attaining a high electrostrain with remarkable temperature stability and minimal hy...Over the past two decades,(K_(0.5)Na_(0.5))NbO_(3)(KNN)-based lead-free piezoelectric ceramics have made significant progress.However,attaining a high electrostrain with remarkable temperature stability and minimal hysteresis under low electric fields has remained a significant challenge.To address this long-standing issue,we have employed a collaborative approach that combines defect engineering,phase engineering,and relaxation engineering.The LKNNS-6BZH ceramic,when sintered at T_(sint)=1170℃,demonstrates an impressive electrostrain with a d_(33) value of 0.276%and 1379 pm·V^(-1)under 20 kV·cm^(-1),which is comparable to or even surpasses that of other lead-free and Pb(Zr,Ti)O_(3)ceramics.Importantly,the electrostrain performance of this ceramic remains stable up to a temperature of 125℃,with the lowest hysteresis observed at 9.73%under 40 kV·cm^(-1).These excellent overall performances are attributed to the presence of defect dipoles involving V′_(A)-V∙∙_(O) and B′_(Nb)-V∙∙O,the coexistence of R-O-T multiphase,and the tuning of the trade-off between long-range ordering and local heterogeneity.This work provides a lead-free alternative for piezoelectric actuators and a paradigm for designing piezoelectric materials with outstanding comprehensive performance under low electric fields.展开更多
Piezoelectric ceramics provide high strain and large driving forces in actuators.A large electrostrain can be realized by the introduction of point defects such as vacancies,interstitial defects,and substitution defec...Piezoelectric ceramics provide high strain and large driving forces in actuators.A large electrostrain can be realized by the introduction of point defects such as vacancies,interstitial defects,and substitution defects.With Mn doping,a significant increase in the reversible electrostrain from 0.05%to 0.17%could be achieved in potassium niobite lead-free piezoelectric ceramics.The origins of the large electrostrain were analyzed via in situ X-ray diffraction(XRD)under an electric field.The electrostrain and other typical electrical properties of the samples were measured at various temperatures,which enabled the ceramics to perform under a very wide temperature range,such as−80–130℃ for the 0.5 mol%Mn-doped sample with low dielectric loss(≤0.02).More importantly,combined with characterizations of the defect behavior by thermally stimulated depolarization current(TSDC),the failure mechanisms of electrostrain in a hightemperature environment could be revealed,which was associated with synergistic damage to the defects caused by the electric field and high temperature.The results can provide good ideas and a basis for the design of piezoelectric materials with good electrostrain stability over a wide temperature range.展开更多
Owing to the complex composition architecture of these solid solutions,some fundamental issues of the classical(1-x)(Bi_(1/2)Na_(1/2))TiO_(3) -x(Bi_(1/2)K_(1/2))TiO_(3)(BNT-xBKT)binary system,such as details of phase ...Owing to the complex composition architecture of these solid solutions,some fundamental issues of the classical(1-x)(Bi_(1/2)Na_(1/2))TiO_(3) -x(Bi_(1/2)K_(1/2))TiO_(3)(BNT-xBKT)binary system,such as details of phase evolution and optimal Na/K ratio associated with the highest strain responses,remain unresolved.In this work,we systematically investigated the phase evolution of the BNT-xBKT binary solid solution with x ranging from 0.12 to 0.24 using not only routine X-ray diffraction and weak-signal dielectric characterization,but also temperature-dependent polarization versus electric field(P-E)and current versus electric field(I-E)curves.Our results indicate an optimal Na/K ratio of 81/19 based on high-field polarization and elec-trostrain characterizations.As the temperature increased above 100?C,the x¼0.19 composition pro-duces ultrahigh electrostrains(>0.5%)with high thermal stability.The ultrahigh and stable electrostrains were primarily due to the combined effect of electric-field-induced relaxor-to-ferroelectric phase tran-sition and ferroelectric-to-relaxor diffuse phase transition during heating.More specifically,we revealed the relationship between phase evolution and electrostrain responses based on the characteristic tem-peratures determined by both weak-field dielectric and high-field ferroelectric/electromechanical property characterizations.This work not only clarifies the phase evolution in BNT-xBKT binary solid solution,but also paves the way for future strain enhancement through doping strategies.展开更多
(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferr...(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferroelectric features,among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value Suni¼0.51%at electric field of 65 kV/cm,with high piezoelectric stain coefficient d33*of 890 pm/V at 45 kV/cm,while the non-ergodic compositions present unrepeatable large strain response.Based on the electric field-composition phase diagram,the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition.In addition,the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions.This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties.展开更多
(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based lead-free piezoceramics exhibit excellent electric field-induced strain(electrostrain)properties,but often suffer from large hysteresis and poor fatigue resistance,which strongly l...(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based lead-free piezoceramics exhibit excellent electric field-induced strain(electrostrain)properties,but often suffer from large hysteresis and poor fatigue resistance,which strongly limit their applications.Here,<00l>textured Nb5+-doped 0.8(Bi_(0.5)Na_(0.5))TiO_(3)–0.2(Bi_(0.5)K_(0.5))TiO_(3)(0.8BNT–0.2BKT)ceramics with a high degree of texturing(~80%)were prepared by the reactive template grain growth(RTGG)method using Bi4Ti3O12 as a template.By the combination of donor doping in the B-site and the RTGG method,the electrostrain performance achieves a significant enhancement.A high electrostrain of 0.65%and a piezoelectric coefficient(*33 d)of 1083 pm/V with reduced hysteresis at an electric field of 6 kV/mm are obtained.No electrostrain performance degradation is observed after unipolar electric field loading of 10^(5)cycles,showing excellent fatigue endurance.These results indicate that the texturing BNT-based lead-free piezoceramics by the RTGG method is a useful approach to developing eco-friendly actuators.展开更多
Large electrostrains with high temperature stability and low hysteresis are essential for applications in high-precision actuator devices.However,achieving simultaneously all three of the aforementioned features in fe...Large electrostrains with high temperature stability and low hysteresis are essential for applications in high-precision actuator devices.However,achieving simultaneously all three of the aforementioned features in ferroelectric ceramics remains a considerable challenge.In this work,we firstly report a high unipolar electrostrain(0.12%at 60 kV/cm)in(1ex)NaNbO_(3)-x[(Ba0.85Ca0.15)(Zr_(0.1)Ti_(0.9))O_(3)](NN-xBCZT)ferroelectric polycrystalline ceramics with excellent thermal stability(variation less than 10%in the temperature range of 30-160℃)and ultra-low hysteresis(<6%).Secondly,the high-field electrostrain response is dominated by the intrinsic electrostrictive effect,which may account for more than 80%of the electrostrain.Furthermore,due to the thermal stability of the polarization in the pure tetragonal phase,the large electrostrain demonstrates extraordinarily high stability from room temperature to 140℃.Finally,in-situ piezoelectric force microscopy reveals ultra-highly stable domain structures,which also guarantee the thermal stability of the electrostrain in(NN-xBCZT ferroelectrics ceramics.This study not only clarifies the origin of thermally stable electrostrain in NN-xBCZT ferroelectric perovskite in terms of electrostrictive effect,but also provides ideas for developing applicable ferroelectric ceramic materials used in actuator devices with excellent thermal stability.展开更多
Electrobending,an emerging phenomenon in electroactive ceramics,has recently attracted significant interest;however,existing measurement methods often confound electrotensile and electrobending strains,leading to ambi...Electrobending,an emerging phenomenon in electroactive ceramics,has recently attracted significant interest;however,existing measurement methods often confound electrotensile and electrobending strains,leading to ambiguity.This study distinguishes electrotensile and electrobending strains in K_(0.5)Na_(0.5)NbO_(3)(KNN)ceramics by examining their thickness,frequency,temperature,and directional dependency,identifying a critical thickness threshold of 600μm for electrobending in samples of 8.5 mm diameter.This threshold establishes a clear distinction between electrotensile and electrobending within the KNN system and provides a benchmark that can be applied to other systems through similar methodologies.Additionally,new electrobending parameters have been defined to assess bending deformation,addressing recent misinterpretations of“giant strain”and advancing electrostrain research by introducing an electrobending framework.展开更多
Bioinspired soft robots hold great potential to perform tasks in unstructured terrains.Ferroelectric polymers are highly valued in soft robots for their flexibility,lightweight,and electrically controllable deformatio...Bioinspired soft robots hold great potential to perform tasks in unstructured terrains.Ferroelectric polymers are highly valued in soft robots for their flexibility,lightweight,and electrically controllable deformation.However,achieving large strains in ferroelectric polymers typically requires high driving voltages,posing a significant challenge for practical applications.In this study,we investigate the role of crystalline domain size in enhancing the electrostrain performance of the relaxor ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene-fluorinated alkynes)(P(VDFTrFE-CFE-FA)).Leveraging its remarkable inverse piezoelectric coefficient(|d33^(*)|=701 pm V^(-1)),we demonstrate that the planar films exhibit a five times larger bending angle than that of commercial PVDF films at low electric fields.Based on this material,we design a petal-structured soft robot that achieves a curvature of up to 4.5 cm^(-1) at a DC electric field of 30 Vμm^(-1).When integrated into a bipedal soft robot,it manifests outstanding electrostrain performance,achieving rapid locomotion of~19 body lengths per second(BL s^(-1))at 10 Vμm^(-1)(560 Hz).Moreover,the developed robot demonstrates remarkable abilities in climbing slopes and carrying heavy loads.These findings open new avenues for developing low-voltage-driven soft robots with significant promise for practical applications.展开更多
The development of high-strain piezoelectric materials has presented a longstanding challenge,particularly in the development of high-strain polycrystalline lead-free piezoelectric thin films.In this work,we present a...The development of high-strain piezoelectric materials has presented a longstanding challenge,particularly in the development of high-strain polycrystalline lead-free piezoelectric thin films.In this work,we present a strategy for customizing the electrostrain in lead-free thin films through phase transition engineering.In this study,we achieved a high recoverable electrostrain in a Bi_(1/2)Na_(1/2)TiO_(3)–BiAlO_(3)(BNT–BA)film.To accomplish this,ferroelectric BNT and BNT–BA films with identical thicknesses of 500 nm were fabricated on Pt(111)/TiO_(2)/SiO_(2)/Si(100)substrates via a sol-gel method.Compared with the BNT film,the BNT–BA film exhibited a greater polarization response and superior field strength endurance,maintaining the energy storage density beyond the breakdown field strength of the BNT.The BNT–BA film demonstrated a large unipolar strain of S=0.43%with a normalized strain(maximum strain/maximum applied electric field(S_(max)/E_(max)))of 203 pm/V,followed by an effective transverse piezoelectric coefficient(e∗31,f)of~2.48 C/m^(2),which was more than two times greater than the value obtained for BNT(i.e.,maximum strain/maximum applied electric field(S_(max)/E_(max))=72 pm/V and e^(∗)_(31,f)of~1.09 C/m^(2)).This high strain response in the BNT–BA film can be attributed to the electric-field-induced phase transition of the mixed(i.e.,cubic and rhombohedral)phases into rhombohedral and tetragonal phases(mainly the rhombohedral structure),which recover back to the original state when the electric field is removed.These findings suggest new pathways for achieving significant strain levels via alternative mechanisms,potentially enhancing the effectiveness and expanding the applications of piezoelectric materials.展开更多
Bismuth ferriteebased ferroelectric ceramics are considered strong competitors in highetemperature piezoelectric applications that benefits from their high depolarization temperature(Td),but problems of large conducti...Bismuth ferriteebased ferroelectric ceramics are considered strong competitors in highetemperature piezoelectric applications that benefits from their high depolarization temperature(Td),but problems of large conductivity and low piezoelectric coefficient(d33)should be tackled.BiFeO_(3)ePbTiO_(3)ex(Sr0.7Bi0.2,0.1)TiO_(3)(BFePTexSBT)ternary system are designed in this work that successfully resolves this tough paradox.Rietveld refinements show that this system exhibits multiphase coexistence with complex structural transition among rhombohedral,tetragonal and pseudocubic phase.Interestingly,a high Td~320℃ and d33~236℃/N are synergistically optimized in x=0.20 composition near pseudoephase boundary,which are indicated by multiescale techniques(phase structure,dielectric analysis etc.).What'smore,dual electrostrain peaks appear at separate phase boundaries for x=0.20 and 0.66 compositions with distinct piezo/ferroelectric properties.Rayleigh law and piezoelectric force microscopy analysis clarify that the optimal electrostrain performance for both critical compositions are dominated by intrinsic(x=0.20)and extrinsic(x=0.66)contributions,respectively.This work not only provides a new BFePTexSBT system with a high Td and superior d33 that are promising candidates in highetemperature actuator and sensor applications,but also presents a possibility of multiphaseecoexistence established exotic macroscopic performances.展开更多
基金supported by the National Nature Science Foundation(Nos.52372125 and 52333009)the National Key Research and Development Project(Nos.2020YFC1521900 and 2020YFC1521904)+4 种基金the Shaanxi Provincial Science Foundation(No.2021GXLH-01-11)the Yulin Project(No.2022-19-11)the Fundamental Research Funds for the Central Universities(No.D5000230071)the 111 Program(No.B08040)of MOE of Chinasponsored by Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX2024063).
文摘Ferroelectric materials find extensive applications in brake systems due to their capability to convert electrical energy into mechanical energy.Recent research has focused on lead-free materials for their environmentally friendly characteristics.However,they exhibit several challenges such as significant negative strain,limited strain values,and large driving field.In this work,novel preparation techniques(electrospinning)were utilized for BaTiO_(3)to introduce oxygen vacancies and barium defects,facilitating the creation of oriented defect dipoles coupled with an intrinsic electric field(Ei)after poling and aging.Due to the existence of Ei,two minimum points in the strain hysteresis loop were shifted to the same quadrant in the Strain-Electric field space.Thus,when applying an electric field along the Ei direction,negative strain is eliminated.Additionally,the actual electric field is the sum of the applied electric field and Ei,thereby reducing the required driving field of the piezoelectric.The stretching of defect dipoles under the electric field further amplified the total strain.Through the proposed mechanisms,this work achieved a substantial unipolar electrostrain of 1.04%under a relatively low electric field(30 kV/cm)in BaTiO_(3).This work successfully addressed the challenges of high-driving electric fields,limited strain values,and negative strain,providing a comprehensive approach for improving field-induced strain performance through point defect engineering in ferroelectric materials.
基金supported by the National Natural Science Foundation of China(Nos.11672264,11972320)the Zhejiang Provincial Natural Science Foundation(No.LZ17A020001)。
文摘The ferroelectric superlattices have been widely studied due to their distinguished electromechanical coupling properties.Under different biaxial mismatch strains,ferroelectric superlattices exhibit different domain structures and electromechanical coupling properties.A three-dimensional phase field model is employed to investigate the detailed domain evolution and electromechanical properties of the PbTiO_(3)/SrTiO_(3)(PTO/STO)superlattices with different biaxial mismatch strains.The phase field simulations show that the ferroelectric superlattice exhibits large electrostrain in the stacking direction when an external field is applied.Under a large compressive mismatch strain,vortex domains appear in ferroelectric layers with the thickness of 4 nm.The vortex domains become stable cdomain under a large external electric field,which remains when the electric field is removed.When the initial compressive mismatch strain decreases gradually,the waved or a1/a2 domains replaces the initial vortex domains in the absence of electric field.The fully polarized c-domain by a large electric field switches to diagonal direction domain or a/c domain when the electric field is small.Furthermore,when a biaxial tensile strain is applied to the superlattice,ferroelectric domains switch back to the initial a1/a2 twin-like domain structure,resulting in the recoverable and large electrostrain.This provides an effective way to obtain the large and recoverable electrostrain for the engineering application.
基金supported by the Natural Science Foundation of Shandong Province,China(Nos.ZR2020ME033 and ZR2020ME031)Research Foundation of the Liaocheng University(No.318011906)+1 种基金Shandong College Students’Innovation and Entrepreneurship Training Program(No.S202210447017)the Undergraduate Training Programs for Innovation and Entrepreneurship of the Liaocheng University(No.cxcy2022022).Di Wang and Jiaqi Zhao contributed equally to this work.
文摘The development of multifunctional materials with optical and electrical properties has become a research hotspot in recent years.In this work,multifunctional 0.935(Bi_(0:5)Na_(0:5))TiO_(3)–0.065BaTiO_(3)(BNT–BT)-based ferroelectric ceramics doped with small amounts of CaMAlO_(4)(M=Dy,Ho)were prepared,and the effect of CaMAlO_(4)on the electrostrain and photoluminescence properties of the ceramics was studied.The results showed that the CaMAlO_(4)addition weakened the ferroelectric properties of the BNT–BT matrix,and promoted the improvement of the electrostrain performance.For samples doped with 1.5 mol%CaMAlO_(4),the unipolar strain Suni reached the largest values,which were 0.33%(M=Dy)and 0.38%(M=Ho)under an electric field of 70 kV/cm,corresponding to a large signal d^(*)_(33)(Smax=Emax)of 471 pm/V(M=Dy)and 543 pm/V(M=Ho),respectively.In addition,due to the existing Dy^(3+)and Ho^(3+)luminescent ions,the modified samples exhibited excellent photoluminescence performance,which exhibited bright yellow emission(M=Dy)and green emission eM=HoT under the blue excitation.Due to their multifunctional features,these materials have potential applications as“on-off”actuators,optical-electro integration and coupling devices.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.52032007 and 52072028)the National Key R&D Program(No.2022YFB3807400)+1 种基金the Basic Science Center Project of National Natural Science Foundation of China(No.52388201)Tsinghua University-Toyota Research Center.
文摘Over the past two decades,(K_(0.5)Na_(0.5))NbO_(3)(KNN)-based lead-free piezoelectric ceramics have made significant progress.However,attaining a high electrostrain with remarkable temperature stability and minimal hysteresis under low electric fields has remained a significant challenge.To address this long-standing issue,we have employed a collaborative approach that combines defect engineering,phase engineering,and relaxation engineering.The LKNNS-6BZH ceramic,when sintered at T_(sint)=1170℃,demonstrates an impressive electrostrain with a d_(33) value of 0.276%and 1379 pm·V^(-1)under 20 kV·cm^(-1),which is comparable to or even surpasses that of other lead-free and Pb(Zr,Ti)O_(3)ceramics.Importantly,the electrostrain performance of this ceramic remains stable up to a temperature of 125℃,with the lowest hysteresis observed at 9.73%under 40 kV·cm^(-1).These excellent overall performances are attributed to the presence of defect dipoles involving V′_(A)-V∙∙_(O) and B′_(Nb)-V∙∙O,the coexistence of R-O-T multiphase,and the tuning of the trade-off between long-range ordering and local heterogeneity.This work provides a lead-free alternative for piezoelectric actuators and a paradigm for designing piezoelectric materials with outstanding comprehensive performance under low electric fields.
基金supported by the National Natural Science Foundation of China(Grant Nos.12135019 and 52202154)the 2115 Talent Development Program of China Agricultural University,the Scientific Research Start-up Fund for Outstanding Talent of China Agricultural University,Chinese Universities Scientific Fund,and High-performance Computing Platform of China Agricultural University。
文摘Piezoelectric ceramics provide high strain and large driving forces in actuators.A large electrostrain can be realized by the introduction of point defects such as vacancies,interstitial defects,and substitution defects.With Mn doping,a significant increase in the reversible electrostrain from 0.05%to 0.17%could be achieved in potassium niobite lead-free piezoelectric ceramics.The origins of the large electrostrain were analyzed via in situ X-ray diffraction(XRD)under an electric field.The electrostrain and other typical electrical properties of the samples were measured at various temperatures,which enabled the ceramics to perform under a very wide temperature range,such as−80–130℃ for the 0.5 mol%Mn-doped sample with low dielectric loss(≤0.02).More importantly,combined with characterizations of the defect behavior by thermally stimulated depolarization current(TSDC),the failure mechanisms of electrostrain in a hightemperature environment could be revealed,which was associated with synergistic damage to the defects caused by the electric field and high temperature.The results can provide good ideas and a basis for the design of piezoelectric materials with good electrostrain stability over a wide temperature range.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51772239 and 51761145024)the Fundamental Research Funds for the Central Universities(XJTU)。
文摘Owing to the complex composition architecture of these solid solutions,some fundamental issues of the classical(1-x)(Bi_(1/2)Na_(1/2))TiO_(3) -x(Bi_(1/2)K_(1/2))TiO_(3)(BNT-xBKT)binary system,such as details of phase evolution and optimal Na/K ratio associated with the highest strain responses,remain unresolved.In this work,we systematically investigated the phase evolution of the BNT-xBKT binary solid solution with x ranging from 0.12 to 0.24 using not only routine X-ray diffraction and weak-signal dielectric characterization,but also temperature-dependent polarization versus electric field(P-E)and current versus electric field(I-E)curves.Our results indicate an optimal Na/K ratio of 81/19 based on high-field polarization and elec-trostrain characterizations.As the temperature increased above 100?C,the x¼0.19 composition pro-duces ultrahigh electrostrains(>0.5%)with high thermal stability.The ultrahigh and stable electrostrains were primarily due to the combined effect of electric-field-induced relaxor-to-ferroelectric phase tran-sition and ferroelectric-to-relaxor diffuse phase transition during heating.More specifically,we revealed the relationship between phase evolution and electrostrain responses based on the characteristic tem-peratures determined by both weak-field dielectric and high-field ferroelectric/electromechanical property characterizations.This work not only clarifies the phase evolution in BNT-xBKT binary solid solution,but also paves the way for future strain enhancement through doping strategies.
基金supported by the National Natural Science Foundation of China(51672220,51902258,51972265)Fundamental Research Funds for the Central Universities(3102019GHXM002)+2 种基金State Key Laboratory of Solidification Processing Project(2019-TZ-04)of China,China Postdoctoral Science Foundation(2019M653729)Natural Science Foundation of Shaanxi Province(2019JQ-621)the Shaanxi Province Postdoctoral Science Foundation(2017BSHEDZZ07).
文摘(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferroelectric features,among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value Suni¼0.51%at electric field of 65 kV/cm,with high piezoelectric stain coefficient d33*of 890 pm/V at 45 kV/cm,while the non-ergodic compositions present unrepeatable large strain response.Based on the electric field-composition phase diagram,the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition.In addition,the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions.This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties.
基金supported by the National Natural Science Foundation of China(52172135)the Youth Top Talent Project of the National“Ten Thousand Talents Program”(2021-527-07)the Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(2021B1515020083 and 2022B1515020070).
文摘(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based lead-free piezoceramics exhibit excellent electric field-induced strain(electrostrain)properties,but often suffer from large hysteresis and poor fatigue resistance,which strongly limit their applications.Here,<00l>textured Nb5+-doped 0.8(Bi_(0.5)Na_(0.5))TiO_(3)–0.2(Bi_(0.5)K_(0.5))TiO_(3)(0.8BNT–0.2BKT)ceramics with a high degree of texturing(~80%)were prepared by the reactive template grain growth(RTGG)method using Bi4Ti3O12 as a template.By the combination of donor doping in the B-site and the RTGG method,the electrostrain performance achieves a significant enhancement.A high electrostrain of 0.65%and a piezoelectric coefficient(*33 d)of 1083 pm/V with reduced hysteresis at an electric field of 6 kV/mm are obtained.No electrostrain performance degradation is observed after unipolar electric field loading of 10^(5)cycles,showing excellent fatigue endurance.These results indicate that the texturing BNT-based lead-free piezoceramics by the RTGG method is a useful approach to developing eco-friendly actuators.
基金supported by the National Natural Science Foundation of China(Grant Nos.52172127 and 52072092)the International Cooperation Project of Shaanxi Province(Grant No.2022KWZ-22)+1 种基金the National Key Research and Development Program of China(Grant Nos.2021YFE0115000 and SQ2021YFB380003202)the Youth Innovation Team of Shaanxi Universities and Scientific Research Program Funded by Shaanxi Provincial Education Department(Grant No.21JP104)。
文摘Large electrostrains with high temperature stability and low hysteresis are essential for applications in high-precision actuator devices.However,achieving simultaneously all three of the aforementioned features in ferroelectric ceramics remains a considerable challenge.In this work,we firstly report a high unipolar electrostrain(0.12%at 60 kV/cm)in(1ex)NaNbO_(3)-x[(Ba0.85Ca0.15)(Zr_(0.1)Ti_(0.9))O_(3)](NN-xBCZT)ferroelectric polycrystalline ceramics with excellent thermal stability(variation less than 10%in the temperature range of 30-160℃)and ultra-low hysteresis(<6%).Secondly,the high-field electrostrain response is dominated by the intrinsic electrostrictive effect,which may account for more than 80%of the electrostrain.Furthermore,due to the thermal stability of the polarization in the pure tetragonal phase,the large electrostrain demonstrates extraordinarily high stability from room temperature to 140℃.Finally,in-situ piezoelectric force microscopy reveals ultra-highly stable domain structures,which also guarantee the thermal stability of the electrostrain in(NN-xBCZT ferroelectrics ceramics.This study not only clarifies the origin of thermally stable electrostrain in NN-xBCZT ferroelectric perovskite in terms of electrostrictive effect,but also provides ideas for developing applicable ferroelectric ceramic materials used in actuator devices with excellent thermal stability.
基金supported by the National Natural Science Foundation of China(No.52172135)the Youth Top Talent Project of the National Special Support Program(No.2021-527-07)+2 种基金the Leading Talent Project of the National Special Support Program(No.2022WRLJ003)the Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(Nos.2022B1515020070 and 2021B1515020083)the Young Elite Scientists Sponsorship Program for PhD Student by China Association for Science and Technology.
文摘Electrobending,an emerging phenomenon in electroactive ceramics,has recently attracted significant interest;however,existing measurement methods often confound electrotensile and electrobending strains,leading to ambiguity.This study distinguishes electrotensile and electrobending strains in K_(0.5)Na_(0.5)NbO_(3)(KNN)ceramics by examining their thickness,frequency,temperature,and directional dependency,identifying a critical thickness threshold of 600μm for electrobending in samples of 8.5 mm diameter.This threshold establishes a clear distinction between electrotensile and electrobending within the KNN system and provides a benchmark that can be applied to other systems through similar methodologies.Additionally,new electrobending parameters have been defined to assess bending deformation,addressing recent misinterpretations of“giant strain”and advancing electrostrain research by introducing an electrobending framework.
基金National Natural Science Foundation of China,Grant/Award Number:U2330120Natural Science Foundation of Sichuan Province of China,Grant/Award Number:2023NSFSC0313Basic Research Cultivation Project of Southwest Jiaotong University,Grant/Award Number:2682023KJ024。
文摘Bioinspired soft robots hold great potential to perform tasks in unstructured terrains.Ferroelectric polymers are highly valued in soft robots for their flexibility,lightweight,and electrically controllable deformation.However,achieving large strains in ferroelectric polymers typically requires high driving voltages,posing a significant challenge for practical applications.In this study,we investigate the role of crystalline domain size in enhancing the electrostrain performance of the relaxor ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene-fluorinated alkynes)(P(VDFTrFE-CFE-FA)).Leveraging its remarkable inverse piezoelectric coefficient(|d33^(*)|=701 pm V^(-1)),we demonstrate that the planar films exhibit a five times larger bending angle than that of commercial PVDF films at low electric fields.Based on this material,we design a petal-structured soft robot that achieves a curvature of up to 4.5 cm^(-1) at a DC electric field of 30 Vμm^(-1).When integrated into a bipedal soft robot,it manifests outstanding electrostrain performance,achieving rapid locomotion of~19 body lengths per second(BL s^(-1))at 10 Vμm^(-1)(560 Hz).Moreover,the developed robot demonstrates remarkable abilities in climbing slopes and carrying heavy loads.These findings open new avenues for developing low-voltage-driven soft robots with significant promise for practical applications.
基金support of the Priority Research Centers Program and the Basic Science Research Program through the National Research Foundation of Korea(NRF),funded by the Ministry of Education(Nos.NRF2019R1A6A1A11053838 and RS-2023-00245221)Aman Ullah acknowledges the support of the Higher Education Commission of Islamabad,Pakistan,under the National Research Program for Universities-NRPU(20-17573/NRPU/R&D/HEC/2021)Muhammad Sheeraz acknowledges support from the Basic Science Research Program through NRF(No.RS-2023-00249613).
文摘The development of high-strain piezoelectric materials has presented a longstanding challenge,particularly in the development of high-strain polycrystalline lead-free piezoelectric thin films.In this work,we present a strategy for customizing the electrostrain in lead-free thin films through phase transition engineering.In this study,we achieved a high recoverable electrostrain in a Bi_(1/2)Na_(1/2)TiO_(3)–BiAlO_(3)(BNT–BA)film.To accomplish this,ferroelectric BNT and BNT–BA films with identical thicknesses of 500 nm were fabricated on Pt(111)/TiO_(2)/SiO_(2)/Si(100)substrates via a sol-gel method.Compared with the BNT film,the BNT–BA film exhibited a greater polarization response and superior field strength endurance,maintaining the energy storage density beyond the breakdown field strength of the BNT.The BNT–BA film demonstrated a large unipolar strain of S=0.43%with a normalized strain(maximum strain/maximum applied electric field(S_(max)/E_(max)))of 203 pm/V,followed by an effective transverse piezoelectric coefficient(e∗31,f)of~2.48 C/m^(2),which was more than two times greater than the value obtained for BNT(i.e.,maximum strain/maximum applied electric field(S_(max)/E_(max))=72 pm/V and e^(∗)_(31,f)of~1.09 C/m^(2)).This high strain response in the BNT–BA film can be attributed to the electric-field-induced phase transition of the mixed(i.e.,cubic and rhombohedral)phases into rhombohedral and tetragonal phases(mainly the rhombohedral structure),which recover back to the original state when the electric field is removed.These findings suggest new pathways for achieving significant strain levels via alternative mechanisms,potentially enhancing the effectiveness and expanding the applications of piezoelectric materials.
基金supported by National Natural Science Foundation of China(Nos.12104001,12174001 and 51872001)Anhui Provincial Natural Science Foundation(No.2008085QE205)+1 种基金Anhui Provincial highereeducation Natural Science research project(KJ2020A0019)the Open Project Program of State Key Laboratory for Mechanical Behavior of Materials(20212313).
文摘Bismuth ferriteebased ferroelectric ceramics are considered strong competitors in highetemperature piezoelectric applications that benefits from their high depolarization temperature(Td),but problems of large conductivity and low piezoelectric coefficient(d33)should be tackled.BiFeO_(3)ePbTiO_(3)ex(Sr0.7Bi0.2,0.1)TiO_(3)(BFePTexSBT)ternary system are designed in this work that successfully resolves this tough paradox.Rietveld refinements show that this system exhibits multiphase coexistence with complex structural transition among rhombohedral,tetragonal and pseudocubic phase.Interestingly,a high Td~320℃ and d33~236℃/N are synergistically optimized in x=0.20 composition near pseudoephase boundary,which are indicated by multiescale techniques(phase structure,dielectric analysis etc.).What'smore,dual electrostrain peaks appear at separate phase boundaries for x=0.20 and 0.66 compositions with distinct piezo/ferroelectric properties.Rayleigh law and piezoelectric force microscopy analysis clarify that the optimal electrostrain performance for both critical compositions are dominated by intrinsic(x=0.20)and extrinsic(x=0.66)contributions,respectively.This work not only provides a new BFePTexSBT system with a high Td and superior d33 that are promising candidates in highetemperature actuator and sensor applications,but also presents a possibility of multiphaseecoexistence established exotic macroscopic performances.
