The inefficient separation of photogenerated carriers has become a serious problem that limits the photoelectrochemical(PEC)performance of semiconductors.Herein,a sol-gel method was used to prepare BiFeO_(3) ferroelec...The inefficient separation of photogenerated carriers has become a serious problem that limits the photoelectrochemical(PEC)performance of semiconductors.Herein,a sol-gel method was used to prepare BiFeO_(3) ferroelectric thin films with FTO and FTO/Au as substrates,respectively.The polarization electric field of the ferroelectric can more effectively separate the carriers generated in the photoelectrode.Meanwhile,the introduction of an Au buffer layer can reduce the resistance in the process of charge transfer,accelerate the carrier migration,and enhance the efficiency of the charge separation.Under light irradiation,Au/BiFeO_(3) photoelectrode exhibited an extraordinary improvement in PEC water splitting compared with BiFeO_(3).In addition,the ferroelectric polarization electric field causes band bending,which further accelerates the separation of electrons and holes and improves the PEC performance of the photoelectrode.This work promotes the effective application of ferroelectric films in PEC water splitting.展开更多
Ferroelectric materials have many interesting physical properties such as ferroelectricity, pyroelectricity, piezoelectricity, and opto-electricity, and applying ferroelectric materials in the forms of thin and thick ...Ferroelectric materials have many interesting physical properties such as ferroelectricity, pyroelectricity, piezoelectricity, and opto-electricity, and applying ferroelectric materials in the forms of thin and thick films and integrating them on the silicon substrate as electronic and MEMS devices is a very attractive research area and challenging. In this paper, we report our research works on ferroelectric MEMS and ferroelectric films for electronic device applications. Pyroelectric thin film infrared sensors have been made, characterized, and a 32×32 array with its size of 1cm×1cm has been obtained on Si membrane. Ferroelectric thin films in amorphous phase have been applied to make silicon based hydrogen gas sensors with the metal/amorphous ferroelectric film/metal device structure, and its turn-on voltage of about 4.5V at ~1000 ppm in air is about 7 times of the best value reported in the literature. For the application of electron emission flat panel display, ferroelectric BST thin films with excess Ti concentrations have been coated on Si tips, the threshold voltage of those ferroelectric film coated tips has been reduced about one order from ~70 V/μm to 4~10 V/μm for different Ti concentrations, and however, the electron emission current density has been increased at least 3~4 order for those coated tips compared to that of the bare Si tips. To fulfill in the thickness gap between thin film of typical ~1 μm made by PVD/CVD and polished ceramic wafer of ~50 μm from the bulk, piezoelectric films with thickness in a range of 1~30 μm have been successfully deposited on Si substrate at a low temperature of 650oC by a novel hybridized deposition technique, and piezoelectric MEMS ultrasonic arrays have been very recently obtained with the sound pressure level up to ~120 dB. More detailed results will be presented and mechanisms will be discussed.展开更多
The size effects of the critical behaviors for the systems of interacting spins are discussed extensively inliterature.In this paper,the finite-size dependence of the critical temperature and susceptibility of the fer...The size effects of the critical behaviors for the systems of interacting spins are discussed extensively inliterature.In this paper,the finite-size dependence of the critical temperature and susceptibility of the ferroelectric thinfilm are investigated numerically based on the four-state Potts model with the nearest-neighbor interactions between thedipole moments.The four orientations of the domains exist in the ferroelectric film and the movement of the domainwalls determines the polarization switching process besides the boundary conditions of the film.The critical exponentsare obtained and our investigations show that the boundary conditions play the important roles for the ferroelectricproperties of the thin films and the critical behavior of the thin films strongly depends on the feature of the surface.展开更多
Many distinguished properties of epitaxial ferroelectric thin films can be tunable through the misfit strain.The strain tunability of ferroelectric and dielectric properties in epitaxial lead titanate ultrathin films ...Many distinguished properties of epitaxial ferroelectric thin films can be tunable through the misfit strain.The strain tunability of ferroelectric and dielectric properties in epitaxial lead titanate ultrathin films is numerically investigated by using a phase field model,in which the surface effect of polarization is taken into account.The response of polarization to the applied electric field in the thickness direction is examined with different misfit strains at room temperature.It is found that a co...展开更多
In the present work,the comparative study of the electric response of Sn_(2)P_(2)S_(6) films to the visible light action was carried out without and under external electric field.The light flux modulated by a chopper ...In the present work,the comparative study of the electric response of Sn_(2)P_(2)S_(6) films to the visible light action was carried out without and under external electric field.The light flux modulated by a chopper induces the integral response comprising time-dependent photoelectric and photovoltaic components.It was shown that spontaneous polarization influences the electric response characteristics.展开更多
Effective tuning of nanoscale domain structures provides fundamental basis for controlling and engineering of various functionalities in ferroelectric materials.In this work,we demonstrate the precise patterning of na...Effective tuning of nanoscale domain structures provides fundamental basis for controlling and engineering of various functionalities in ferroelectric materials.In this work,we demonstrate the precise patterning of nanoscopic domain structures in as-grown epitaxial PbTiO_(3)(PTO)films by merely introducing an ultrathin pre-patterned doping layer(e.g.,Fe-doped PTO).The doping layer can effectively reverse the interfacial built-in bias,consequent to a reversed initial polarization reorientation in the as-grown film,which makes it possible to transfer the nano-patterns in the doping layer into the domain structure of ferroelectric films.For instance,we have successfully fabricated large area ordered array of nanoscale cylindrical domains(downward polarization)embedded in the matrix domain with opposite polarization(upward polarization)in PTO film.These nanoscale cylinder domains also allow deterministic and reversible erasure and creation induced by biased tip scanning.The results provide an effective pathway for on-demand patterning of large area nanoscale domains in the as-grown films,which may find applications in a wide range of nanoelectronic devices.展开更多
The controllable manipulation of polar topological structures(e.g.skyrmion bubble)in ferroelectric materials have been considered as a cornerstone for future programmable nano-electronics.Here,we present the effective...The controllable manipulation of polar topological structures(e.g.skyrmion bubble)in ferroelectric materials have been considered as a cornerstone for future programmable nano-electronics.Here,we present the effective creation and erasure of polar bubble states PbTiO_(3)(PTO)multilayers trigged by mechanical stress and light illumination,respectively.It was found that applying atomic force microscope(AFM)tip force can induced formation of nanoscale bubble domains from the initial monodomain state.Moreover,the created bubble domain can be eliminated by exposure to ultraviolet or infrared light illumination.The above results can be understood by modulation of depolarization screening charges and bias fields,as reflected by scanning Kelvin potential microscopic(SKPM)observations,whereby the flexoelectric effect from the tip force tends to remove the screening charges on top surface and modulate the bias field that favors the formation of bubble state while light illumination tends to recover the screen charges and favor the monodomain state.The results provide a good example for multi-field manipulation of polar topologies,which might create a new avenue towards the immerging new concept electronic devices.展开更多
Ferroelectrics are an important class of functional materials.Among all their unique properties,the study of their ferroelectric domains and domain walls is of great interest due to their importance in ferroelectric a...Ferroelectrics are an important class of functional materials.Among all their unique properties,the study of their ferroelectric domains and domain walls is of great interest due to their importance in ferroelectric applications.There are many methods to characterize ferroelectric domains,namely,scanning probe microscopy,optical microscopy,electron microscopy,etc.Currently,newly emerged molecular ferroelectrics are attracting much attention from chemists,physicists and researchers in material sciences due to their structural flexibility,light mass,simple fabrication,etc.However,for the characterization of molecular ferroelectric domains,most conventional methods require either a complicated preparation process or direct contact between physical probes and material surfaces,limiting the development of molecular ferroelectric materials.In this report,we have demonstrated that confocal micro-Raman spectroscopy,as a nondestructive and noncontact in-situ method,is very suitable for studying the ferroelectric polarization and structures of domains in molecular ferroelectrics.Taking recently reported molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium(II)(TMCM-CdCl_(3))as an example,the non-180°domains have been characterized and visualized at different temperatures.Such a simple and extendable method requires minimum sample preparation,which would further benefit the research of molecular ferroelectric domain engineering and promote the miniaturization and integration of molecular ferroelectric films.展开更多
Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric fil...Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric films are frequently investigated for photovoltaic applications due to their unique photovoltaic properties and bandgap-independent photovoltage,while the flexoelectric effect is an electromechanical property commonly found in solid dielectrics.Here,we effectively construct a new form of coupled nanogenerator based on a flexible BiFeO_(3) ferroelectric film that combines both flexoelectric and photovoltaic effects to successfully harvest both light and vibration energies.This device converts an alternating current into a direct current and achieves a 6.2% charge enhancement and a 19.3%energy enhancement to achieve a multi-dimensional"1+1>2"coupling enhancement in terms of current,charge and energy.This work proposes a new approach to the coupling of multiple energy harvesting mechanisms in ferroelectric nanogenerators and provides a new strategy to enhance the transduction efficiency of flexible functional devices.展开更多
Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0....Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.展开更多
In this work,we show that a d_(33)~150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE))copolymer films with an arch structure.The copolymer films,which are often thought to be ...In this work,we show that a d_(33)~150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE))copolymer films with an arch structure.The copolymer films,which are often thought to be homogeneous,are in fact inhomogeneous in microstructure and physical properties after film fabrication.Although a large proportion of the copolymer film is nonpolar,as expected in a nonpoled ferroelectric film,the surface regions of the film are spontaneously polarized.We propose that inhomogeneous stress in the surface regions,which is either from the constraint of the substrate or skin layer effect formed during the film fabrication,generates a flexoelectric response and orients the spontaneous polarization of the ferroelectric film.As a result of the polar surface regions,the nonpoled films exhibit a piezoelectric response.The piezoelectric response is further amplified by the special arch structure of the films,leading to the observed large effective piezoelectric response.This study not only discovers the polar surface effect in ferroelectric polymer films,but also proposes an approach to design polymer materials with a strong piezoelectric response.展开更多
Intelligent robots have assisted mankind in achieving and operating thousands of functions,especially with the arrival of the artificial intelligent.However,heat dissipation and thermal management in the intelligent r...Intelligent robots have assisted mankind in achieving and operating thousands of functions,especially with the arrival of the artificial intelligent.However,heat dissipation and thermal management in the intelligent robots remain big challenges,which limit their miniaturization and performance.Electrocaloric(EC)materials,which exhibit temperature change in response to the application or withdrawal of an electric field,open a new strategy for cooling technology and have gained a flurry of research interest in recent years.Toward artificial intelligent self-cooling electronic skins,large-scale flexible materials with high EC effect near room temperature are in demand.Here,we report a large room temperature EC effect in flexible Pb_(0.82)Ba_(0.08)La_(0.1)Zr0.9Ti_(0.1)O_(3)(PBLZT)inorganic thin films via a transfer-free cost-effective sol-gel process,assisted by unique two-dimensional mica substrates.The maximum adiabatic temperature change and isothermal entropy change of the flexible PBLZT thin films reach to 22.5 K and 25.9 J K^(-1) kg^(-1) at room temperature.In particular,the flexible PBLZT thin films exhibit a stable EC effect both under bending state and after bending for 20000 times.Our flexible EC materials offer an alternative strategy to the development of cooling technologies for both artificial intelligent robots and personal wearable cooling devices.展开更多
Dielectric capacitors are the ideal energy storage devices because they have excellent power density,high working voltages,and a long lifespan.With its lower size and better energy storage density,film capacitors make...Dielectric capacitors are the ideal energy storage devices because they have excellent power density,high working voltages,and a long lifespan.With its lower size and better energy storage density,film capacitors make them simpler to incorporate into circuits than traditional dielectric capacitor devices.Lead-free Nb-based perovskite ferroelectric/antiferroelectric films have strong orbital hybridization with O 2p orbitals due to unfilled d orbitals of Nb elements,forming a series of energy storage film materials with potential application value.Here,we provide an overview of the state-of-the-art lead-free Nb-based films for energy storage applications,which include K_(0.5)Na_(0.5)NbO_(3)-based,K_(0.5)Na_(0.5)Bi_(4)NbTi_(3)O_(15)-based,AgNbO_(3)-based and NaNbO_(3)-based films.An overview of the benefits and drawbacks of each kind of Nb-based perovskite ferroelectric/antiferroelectric films is provided,along with a description of the design tactics used to achieve high energy storage performances.展开更多
基金This work was supported by National Natural Science Foundation of China(Grant No.51702130)the Innovation/Entrepreneurship Program of Jiangsu Province and the project of Zhenjiang Key Laboratory of Advanced Sensing Materials and Devices(No.SS2018001)。
文摘The inefficient separation of photogenerated carriers has become a serious problem that limits the photoelectrochemical(PEC)performance of semiconductors.Herein,a sol-gel method was used to prepare BiFeO_(3) ferroelectric thin films with FTO and FTO/Au as substrates,respectively.The polarization electric field of the ferroelectric can more effectively separate the carriers generated in the photoelectrode.Meanwhile,the introduction of an Au buffer layer can reduce the resistance in the process of charge transfer,accelerate the carrier migration,and enhance the efficiency of the charge separation.Under light irradiation,Au/BiFeO_(3) photoelectrode exhibited an extraordinary improvement in PEC water splitting compared with BiFeO_(3).In addition,the ferroelectric polarization electric field causes band bending,which further accelerates the separation of electrons and holes and improves the PEC performance of the photoelectrode.This work promotes the effective application of ferroelectric films in PEC water splitting.
文摘Ferroelectric materials have many interesting physical properties such as ferroelectricity, pyroelectricity, piezoelectricity, and opto-electricity, and applying ferroelectric materials in the forms of thin and thick films and integrating them on the silicon substrate as electronic and MEMS devices is a very attractive research area and challenging. In this paper, we report our research works on ferroelectric MEMS and ferroelectric films for electronic device applications. Pyroelectric thin film infrared sensors have been made, characterized, and a 32×32 array with its size of 1cm×1cm has been obtained on Si membrane. Ferroelectric thin films in amorphous phase have been applied to make silicon based hydrogen gas sensors with the metal/amorphous ferroelectric film/metal device structure, and its turn-on voltage of about 4.5V at ~1000 ppm in air is about 7 times of the best value reported in the literature. For the application of electron emission flat panel display, ferroelectric BST thin films with excess Ti concentrations have been coated on Si tips, the threshold voltage of those ferroelectric film coated tips has been reduced about one order from ~70 V/μm to 4~10 V/μm for different Ti concentrations, and however, the electron emission current density has been increased at least 3~4 order for those coated tips compared to that of the bare Si tips. To fulfill in the thickness gap between thin film of typical ~1 μm made by PVD/CVD and polished ceramic wafer of ~50 μm from the bulk, piezoelectric films with thickness in a range of 1~30 μm have been successfully deposited on Si substrate at a low temperature of 650oC by a novel hybridized deposition technique, and piezoelectric MEMS ultrasonic arrays have been very recently obtained with the sound pressure level up to ~120 dB. More detailed results will be presented and mechanisms will be discussed.
基金the Center for Smart Materials of The Hong Kong Polytechnic University the Earmarked Research Grant(Account No.B-Q 363)allocated by the Hong Kong Research Grants Council
文摘The size effects of the critical behaviors for the systems of interacting spins are discussed extensively inliterature.In this paper,the finite-size dependence of the critical temperature and susceptibility of the ferroelectric thinfilm are investigated numerically based on the four-state Potts model with the nearest-neighbor interactions between thedipole moments.The four orientations of the domains exist in the ferroelectric film and the movement of the domainwalls determines the polarization switching process besides the boundary conditions of the film.The critical exponentsare obtained and our investigations show that the boundary conditions play the important roles for the ferroelectricproperties of the thin films and the critical behavior of the thin films strongly depends on the feature of the surface.
基金the financial support from the National Nature Science Foundation of China (Grants Nos.11002123 and 10832009)Zhejiang Provincial Qianjiang Talent Fund(E9027)Key Innovation Fund(2009R50025)
文摘Many distinguished properties of epitaxial ferroelectric thin films can be tunable through the misfit strain.The strain tunability of ferroelectric and dielectric properties in epitaxial lead titanate ultrathin films is numerically investigated by using a phase field model,in which the surface effect of polarization is taken into account.The response of polarization to the applied electric field in the thickness direction is examined with different misfit strains at room temperature.It is found that a co...
基金This work was supported by Russian Science Foundation(Grant No.15-19-00138).
文摘In the present work,the comparative study of the electric response of Sn_(2)P_(2)S_(6) films to the visible light action was carried out without and under external electric field.The light flux modulated by a chopper induces the integral response comprising time-dependent photoelectric and photovoltaic components.It was shown that spontaneous polarization influences the electric response characteristics.
基金The authors would like to acknowledge the financial support from the National Natural Science Foundation of China(Grant Nos.92163210,11674108,52002134)Funding by Science and Technology Projects in Guangzhou(202201000008)+1 种基金the Science and Technology Planning Project of Guangdong Province(No.2019KQNCX028)the Natural Science Foundation of South China Normal University(No.19KJ01)。
文摘Effective tuning of nanoscale domain structures provides fundamental basis for controlling and engineering of various functionalities in ferroelectric materials.In this work,we demonstrate the precise patterning of nanoscopic domain structures in as-grown epitaxial PbTiO_(3)(PTO)films by merely introducing an ultrathin pre-patterned doping layer(e.g.,Fe-doped PTO).The doping layer can effectively reverse the interfacial built-in bias,consequent to a reversed initial polarization reorientation in the as-grown film,which makes it possible to transfer the nano-patterns in the doping layer into the domain structure of ferroelectric films.For instance,we have successfully fabricated large area ordered array of nanoscale cylindrical domains(downward polarization)embedded in the matrix domain with opposite polarization(upward polarization)in PTO film.These nanoscale cylinder domains also allow deterministic and reversible erasure and creation induced by biased tip scanning.The results provide an effective pathway for on-demand patterning of large area nanoscale domains in the as-grown films,which may find applications in a wide range of nanoelectronic devices.
基金the financial support from the National Key Research and Development Programs of China(Grant Nos.2022YFB3807603)National Natural Science Foundation of China(Grant Nos.92163210,11674108,52002134,U22A20117)+2 种基金Funding by Science and Technology Projects in Guangzhou(202201000008)the Science and Technology Planning Project of Guangdong Province(No.2019KQNCX028)the Natural Science Foundation of South China Normal University(No.19KJ01).
文摘The controllable manipulation of polar topological structures(e.g.skyrmion bubble)in ferroelectric materials have been considered as a cornerstone for future programmable nano-electronics.Here,we present the effective creation and erasure of polar bubble states PbTiO_(3)(PTO)multilayers trigged by mechanical stress and light illumination,respectively.It was found that applying atomic force microscope(AFM)tip force can induced formation of nanoscale bubble domains from the initial monodomain state.Moreover,the created bubble domain can be eliminated by exposure to ultraviolet or infrared light illumination.The above results can be understood by modulation of depolarization screening charges and bias fields,as reflected by scanning Kelvin potential microscopic(SKPM)observations,whereby the flexoelectric effect from the tip force tends to remove the screening charges on top surface and modulate the bias field that favors the formation of bubble state while light illumination tends to recover the screen charges and favor the monodomain state.The results provide a good example for multi-field manipulation of polar topologies,which might create a new avenue towards the immerging new concept electronic devices.
基金supported by the National Key R&D Program of China (No.2021YFA1200700)the National Natural Science Foundation of China (No.21925502)the Fundamental Research Funds for the Central Universities,China.The authors gratefully acknowledge professor Sheng-Ping Guo of Yangzhou University for his help in DFT calculation.
文摘Ferroelectrics are an important class of functional materials.Among all their unique properties,the study of their ferroelectric domains and domain walls is of great interest due to their importance in ferroelectric applications.There are many methods to characterize ferroelectric domains,namely,scanning probe microscopy,optical microscopy,electron microscopy,etc.Currently,newly emerged molecular ferroelectrics are attracting much attention from chemists,physicists and researchers in material sciences due to their structural flexibility,light mass,simple fabrication,etc.However,for the characterization of molecular ferroelectric domains,most conventional methods require either a complicated preparation process or direct contact between physical probes and material surfaces,limiting the development of molecular ferroelectric materials.In this report,we have demonstrated that confocal micro-Raman spectroscopy,as a nondestructive and noncontact in-situ method,is very suitable for studying the ferroelectric polarization and structures of domains in molecular ferroelectrics.Taking recently reported molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium(II)(TMCM-CdCl_(3))as an example,the non-180°domains have been characterized and visualized at different temperatures.Such a simple and extendable method requires minimum sample preparation,which would further benefit the research of molecular ferroelectric domain engineering and promote the miniaturization and integration of molecular ferroelectric films.
基金This work was supported by the National Natural Science Foundation of China(No.52072041)the Beijing Natural Science Foundation(No.JQ21007)the University of Chinese Academy of Sciences(No.Y8540XX2D2).
文摘Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric films are frequently investigated for photovoltaic applications due to their unique photovoltaic properties and bandgap-independent photovoltage,while the flexoelectric effect is an electromechanical property commonly found in solid dielectrics.Here,we effectively construct a new form of coupled nanogenerator based on a flexible BiFeO_(3) ferroelectric film that combines both flexoelectric and photovoltaic effects to successfully harvest both light and vibration energies.This device converts an alternating current into a direct current and achieves a 6.2% charge enhancement and a 19.3%energy enhancement to achieve a multi-dimensional"1+1>2"coupling enhancement in terms of current,charge and energy.This work proposes a new approach to the coupling of multiple energy harvesting mechanisms in ferroelectric nanogenerators and provides a new strategy to enhance the transduction efficiency of flexible functional devices.
基金the National Natural Science Foundation of China under Grant No.51332003 and 51372171。
文摘Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.
基金supported by the National Key Research and Development Program of China(Nos.2017YFA0701301 and 2020YFA0711502).
文摘In this work,we show that a d_(33)~150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE))copolymer films with an arch structure.The copolymer films,which are often thought to be homogeneous,are in fact inhomogeneous in microstructure and physical properties after film fabrication.Although a large proportion of the copolymer film is nonpolar,as expected in a nonpoled ferroelectric film,the surface regions of the film are spontaneously polarized.We propose that inhomogeneous stress in the surface regions,which is either from the constraint of the substrate or skin layer effect formed during the film fabrication,generates a flexoelectric response and orients the spontaneous polarization of the ferroelectric film.As a result of the polar surface regions,the nonpoled films exhibit a piezoelectric response.The piezoelectric response is further amplified by the special arch structure of the films,leading to the observed large effective piezoelectric response.This study not only discovers the polar surface effect in ferroelectric polymer films,but also proposes an approach to design polymer materials with a strong piezoelectric response.
基金the National Natural Science Foundation of China(51602156,51790492 and 11874032)the Natural Science Foundation of Jiangsu Province,China(BK20160824)the Fundamental Research Funds for the Central Universities(30916011208 and 30916011104).
文摘Intelligent robots have assisted mankind in achieving and operating thousands of functions,especially with the arrival of the artificial intelligent.However,heat dissipation and thermal management in the intelligent robots remain big challenges,which limit their miniaturization and performance.Electrocaloric(EC)materials,which exhibit temperature change in response to the application or withdrawal of an electric field,open a new strategy for cooling technology and have gained a flurry of research interest in recent years.Toward artificial intelligent self-cooling electronic skins,large-scale flexible materials with high EC effect near room temperature are in demand.Here,we report a large room temperature EC effect in flexible Pb_(0.82)Ba_(0.08)La_(0.1)Zr0.9Ti_(0.1)O_(3)(PBLZT)inorganic thin films via a transfer-free cost-effective sol-gel process,assisted by unique two-dimensional mica substrates.The maximum adiabatic temperature change and isothermal entropy change of the flexible PBLZT thin films reach to 22.5 K and 25.9 J K^(-1) kg^(-1) at room temperature.In particular,the flexible PBLZT thin films exhibit a stable EC effect both under bending state and after bending for 20000 times.Our flexible EC materials offer an alternative strategy to the development of cooling technologies for both artificial intelligent robots and personal wearable cooling devices.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.12074204,11864028)Natural Science Foundation of Inner Mongolia(Grant No.2022ZD06,2021BS01004,2021BS05006)Foundation of Inner Mongolia University of Technology(ZZ202003,ZY202008).
文摘Dielectric capacitors are the ideal energy storage devices because they have excellent power density,high working voltages,and a long lifespan.With its lower size and better energy storage density,film capacitors make them simpler to incorporate into circuits than traditional dielectric capacitor devices.Lead-free Nb-based perovskite ferroelectric/antiferroelectric films have strong orbital hybridization with O 2p orbitals due to unfilled d orbitals of Nb elements,forming a series of energy storage film materials with potential application value.Here,we provide an overview of the state-of-the-art lead-free Nb-based films for energy storage applications,which include K_(0.5)Na_(0.5)NbO_(3)-based,K_(0.5)Na_(0.5)Bi_(4)NbTi_(3)O_(15)-based,AgNbO_(3)-based and NaNbO_(3)-based films.An overview of the benefits and drawbacks of each kind of Nb-based perovskite ferroelectric/antiferroelectric films is provided,along with a description of the design tactics used to achieve high energy storage performances.