The accepted doping ion in Ti^(4+)-site of PbZr_(y)Ti_(1–y)O_(3)(PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor(Q_(m)),since the acceptor coupled by oxygen vacancy beco...The accepted doping ion in Ti^(4+)-site of PbZr_(y)Ti_(1–y)O_(3)(PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor(Q_(m)),since the acceptor coupled by oxygen vacancy becomes defect dipole,which prevents the domain rotation.In this field,a serious problem is that generally,Qm decreases as the temperature(T)increases,since the oxygen vacancies are decoupled from the defect dipoles.In this work,Q_(m) of Pb_(0.95)Sr_(0.05)(Zr_(0.53)Ti_(0.47))O_(3)(PSZT)ceramics doped by 0.40%Fe_(2)O_(3)(in mole)abnormally increases as T increases,of which the Qm and piezoelectric coefficient(d_(33))at room temperature and Curie temperature(TC)are 507,292 pC/N,and 345℃,respectively.The maximum Qm of 824 was achieved in the range of 120–160℃,which is 62.52%higher than that at room temperature,while the dynamic piezoelectric constant(d_(31))was just slightly decreased by 3.85%.X-ray diffraction(XRD)and piezoresponse force microscopy results show that the interplanar spacing and the fine domains form as temperature increases,and the thermally stimulated depolarization current shows that the defect dipoles are stable even the temperature up to 240℃.It can be deduced that the aggregation of oxygen vacancies near the fine domains and defect dipole can be stable up to 240℃,which pins domain rotation,resulting in the enhanced Q_(m) with the increasing temperature.These results give a potential path to design high Q_(m) at high temperature.展开更多
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
A series of Sr_(1-1.5x)Lu_(x)TiO_(3)(x=0,0.005,0.01,0.015,and 0.02)ceramics was sintered under an air at-mosphere through the solid-state reaction method.The results show that doping with Lu^(3+)consid-erably enhances...A series of Sr_(1-1.5x)Lu_(x)TiO_(3)(x=0,0.005,0.01,0.015,and 0.02)ceramics was sintered under an air at-mosphere through the solid-state reaction method.The results show that doping with Lu^(3+)consid-erably enhances material permittivity.The ceramic with x=0.01 exhibits a colossal permittivity(CP)of~101000 with a tanδof~0.16 at a frequency of 1 kHz,demonstrating enhanced stability over a wide temperature(30-300℃)and frequency(102-106 Hz)range.Based on the analysis of dielectric relaxation,X-ray photoelectron spectroscopy(XPS),and the universal dielectric response law,the CP effect is primarily due to the formation of defect dipoles,which are correlated with the presence of oxygen vacancies,such as Ti^(3+)-V_(O)^(¨)-Ti^(3+),V_(Sr)″-V_(O)^(¨),LuTi′-V_(O)^(¨)-Ti^(3+),and Lu_(Sr)·-Lu_(Ti)′-V_(O)^(¨)-Ti^(3+).These defect dipoles serve to pin electrons,limiting long-range transitions,and enhancing local po-larization.Doping with Lu^(3+)also induces a secondary Lu_(2)Ti_(2)O_(7)phase,which was characterized by X-ray diffraction(XRD)and energy-dispersive X-ray spectroscopy(EDS).The results generated in this study can inform the development and application of new CP materials based on SrTiO_(3).展开更多
PbTiO_(3)-based piezoelectric ceramics are key materials for developing various electromechanical transduc-ers.For high-power ultrasonic transducers,piezoelectric ceramics are required to possess large piezo-electric ...PbTiO_(3)-based piezoelectric ceramics are key materials for developing various electromechanical transduc-ers.For high-power ultrasonic transducers,piezoelectric ceramics are required to possess large piezo-electric coefficient(d_(33))and high mechanical quality factor(Q_(m)).Although acceptor dopants can im-prove Q_(m),they also deteriorate d_(33).If suitable piezoelectricity-beneficial donor dopants can be intro-duced into acceptor-doped ceramics,it is very possible to obtain large d_(33)and high Q_(m)simultaneously in donor and acceptor co-doped ceramics.In this work,a series of x mol%Sm and y mol%Mn co-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-30PbTiO_(3)(PMN-30PT:x Sm,y Mn)ceramics were prepared by the solid-phase sintered method.The crystal structure,local domain structure and electromechanical properties were sys-tematically analyzed.Optimal performances were obtained in PMN-30PT:2.5Sm,1-2Mn ceramics with d_(33)=860-543 pC/N,Q_(m)=495-754,and dielectric loss tanδ=0.0055-0.0086.This high performance origi-nates from the combined effects of(Mn″Ti−V_(o)^(••))^(×)defect dipoles and the local structural heterogeneity.展开更多
Inter-growth bismuth layer-structured ferroelectrics（BLSFs）, Bi_4Ti_3O_（12）-Na_（0.5）Bi_（4.5）Ti_4O_（15）（BIT-NBT）, were successfully synthesized using the traditional solid-state reaction method. X-ray diffr...Inter-growth bismuth layer-structured ferroelectrics（BLSFs）, Bi_4Ti_3O_（12）-Na_（0.5）Bi_（4.5）Ti_4O_（15）（BIT-NBT）, were successfully synthesized using the traditional solid-state reaction method. X-ray diffraction（XRD） Rietveld refinements were conducted using GSAS software. Good agreement and low residual are obtained. The XRD diffraction peaks can be well indexed into I2 cm space group. The inter-growth structure was further observed in the high-resolution TEM image. Dielectric and impedance properties were measured and systematically analyzed. At the temperature range 763-923 K（below T_c）, doubly ionized oxygen vacancies（OVs） are localized and the short-range hopping leads to the relaxation processes with an activation energy of 0.79-1.01 eV. Above T_c, the doubly charged OVs are delocalized and become free ones, which contribute to the long-range dc conduction. The reduction in relaxation species gives rise to a higher relaxation activation energy ~ 1.6 eV.展开更多
The poor temperature stability of the BaTiO_(3) ceramic has always been the main problem limiting their application.This situation has been improved but sacrifices the intrinsic polarization,which significantly reduce...The poor temperature stability of the BaTiO_(3) ceramic has always been the main problem limiting their application.This situation has been improved but sacrifices the intrinsic polarization,which significantly reduces the dielectric constant.In this work,the mechanism of multiple polarization was creatively introduced,and the temperature stability and dielectric properties of BaTiO_(3)-based ceramics are simultaneously enhanced.In particular,the Ba_(0.9925)Bi_(0.005)Ti_(0.995)Ca_(0.005)O_(2.995)(BBTC0.5)ceramic sample achieved excellent temperature stability(-14.8%to 8.85%)over an ultra-wide temperature range(-47 to 400℃)and exhibited colossal permittivity(27,125,25℃,1 kHz)and low dielectric loss(0.07,25℃,1 kHz).The dielectric properties,complex impedance spectra combined with XPS results indicate that the defective dipole clusters(Ti^(3+)-V_(O)-Ti^(3+),Bi_(Ba) and Ca″_(Ti)-V_(O))along with surface effects lead to colossal permittivity effect.More importantly,SEM images show the presence of the second phase at grain boundaries,which prevent the carriers within the grains from accumulating at the grain boundaries.As a result,the dielectric loss was reduced and the temperature stability was further extended.This strategy breaks the traditional limitation of single/noncomprehensive enhancement by singlepolarization mechanism,and is of great theoretical and practical significance to promote the research and application of high-performance BaTiO_(3)-based ceramic materials.展开更多
Antiferroelectric materials represented by PbZrO_(3)(PZO)have excellent energy storage performance and are expected to be candidates for dielectric capacitors.It remains a challenge to further enhance the effective en...Antiferroelectric materials represented by PbZrO_(3)(PZO)have excellent energy storage performance and are expected to be candidates for dielectric capacitors.It remains a challenge to further enhance the effective energy storage density and efficiency of PZO-based antiferroelectricfilms through domain engineering.In this work,the effects of three variables,misfit strain between the thinfilm and substrate,defect dipoles doping,andfilm thickness,on the domain structure and energy storage performance of PZO-based antiferroelectric materials are comprehensively investigated via phase-field simulations.The results show that applying tensile strain to thefilms can effectively increase the transition electricfield from antiferroelectric to ferroelectric.In addition,the introduction of defect dipoles while applying tensile strain can significantly reduce the hysteresis and improve energy storage efficiency.Ultimately,a recoverable energy density of 38.3 J/cm^(3)and an energy storage efficiency of about 89.4%can be realized at 1.5%tensile strain and 2%defect dipole concentration.Our work provides a new idea for the preparation of antiferroelectric thinfilms with high energy storage density and efficiency by domain engineering modulation.展开更多
Electrocaloric(EC)refrigeration,which employs ferroelectric(FE)ceramics as a working medium,is regarded as a promising green refrigeration technology that could potentially replace vapor-compression refrigeration.One ...Electrocaloric(EC)refrigeration,which employs ferroelectric(FE)ceramics as a working medium,is regarded as a promising green refrigeration technology that could potentially replace vapor-compression refrigeration.One of the principal considerations in EC application is the capacity to attain high EC strength near room temperature.In this work,we investigated the EC effect in Sm/Mn co-doped BaTiO_(3)[(Ba_(1-1.5x)Sm_(x))(Ti_(0.99)Mn_(0.01))O_(3)]ceramics.As the smallest trivalent ion that can totally occupy the A site,Sm^(3+)is not only capable of shifting the Curie temperature but also of optimizing the EC effect.Furthermore,the introduction of the Mn element into the matrix results in the formation of defect dipoles,which also serves to enhance the EC performance.Therefore,large EC strengths of △T/△E=0.49Kmm kV^(-1)(@51℃),0.34Kmm kV^(-1)(@39℃)and 0.21Kmm kV^(-1)(@30℃)were,respectively,achieved in x=0.05-0.07 ceramics,demonstrating the potential for future refrigeration applications.展开更多
Piezoelectric PZT ceramics with high piezoelectric properties and good thermal stability are urgently desired concerning the practical application.New compositions of LiNbO_(3) modified Pb(Ni_(1/3)Nb_(2/3))O_(3)single...Piezoelectric PZT ceramics with high piezoelectric properties and good thermal stability are urgently desired concerning the practical application.New compositions of LiNbO_(3) modified Pb(Ni_(1/3)Nb_(2/3))O_(3)single bondPbZrO_(3)single bondPbTiO_(3) ceramics have been prepared in this study.The effects of the introduction of the LiNbO_(3) on the system were comprehensively investigated in terms of the phase structure,microstructure,electric properties,and thermal stability behavior of the ceramics.All compositions are located in the morphotropic phase boundary(MPB)region,and the ratio of the rhombohedral(R)phase increases obviously with the increase of LiNbO_(3) concentration.With increasing the LiNbO_(3) content,the piezoelectric properties were significantly enhanced.The sample added with 2%(in mole)LiNbO_(3) shows excellent electric properties,including T_(m)=185℃,εr=5,643,k_(p)=0.626,Q_(m)=51,d_(33)=902 pC/N.More importantly,no thermal depolarization behavior was observed in the temperature range of 25–100℃.For PNN-PZT-x%LN ceramics,which is mainly attributed to the pinning effect resulted by the(Li_(Pb)-Nb_(Zr/Ti)) defect dipoles.展开更多
High-performance Pb(Zr_(1−x)Ti_(x))O_(3)(PZT)piezoceramics are urgently desired by the market in view of their expanded operating temperature range,reduced property temperature dependence,and enhanced sensitivity and ...High-performance Pb(Zr_(1−x)Ti_(x))O_(3)(PZT)piezoceramics are urgently desired by the market in view of their expanded operating temperature range,reduced property temperature dependence,and enhanced sensitivity and acoustic power.In this work,we reported a kind of low-cost and high-performance 0.06BiYbO_(3)–0.94Pb(Zr_(0.48)Ti_(0.52))O_(3) ternary piezoceramics;the modifying effects of La_(2)O_(3) on this perovskite system were investigated in terms of the structures,electrical properties,and thermal depolarization behaviors of ceramics.The field-dependent dielectric and conduction properties indicated that there are close correlations among oxygen vacancies(VO),conducting electrons,and intrinsic conduction process.The degradation in ferroelectric properties observed in those samples doped with more than 0.15 wt%of La_(2)O_(3) indicated that the occupying mechanisms of La^(3+)changed from the donor substitution for Pb^(2+)to the isovalent substitution for Bi^(3+).The thermally depoling micromechanisms of ceramics were revealed from the thermodynamic processes of defect dipoles and intrinsic dipoles within ferroelectric domains.The sample doped with 0.15 wt%of La_(2)O_(3) shows excellent electrical properties with TC=387℃,d33=332 pC/N,TKε=5.81×10^(−3)℃−1,Pr=20.66μC/cm^(2),Td=356℃.The significantly enhanced electrical properties and thermal depolarization temperature benefited from the donor substitution of La3+,decreasing the oxygen vacancy concentration in the lattice and possibly optimizing the ferroelectric domain structure of ceramics.展开更多
Ba(Mg_(1/3)Nb_(2/3))O_(3)(BMN)doped and undoped B_(0.45)Sr_(0.55)TiO_(3)(BST)thin films were deposited via radio frequency magnetron sputtering on PUTiO_(2)/SiO_(2)/Al_(2)O_(3) substrates.The surface morphology and ch...Ba(Mg_(1/3)Nb_(2/3))O_(3)(BMN)doped and undoped B_(0.45)Sr_(0.55)TiO_(3)(BST)thin films were deposited via radio frequency magnetron sputtering on PUTiO_(2)/SiO_(2)/Al_(2)O_(3) substrates.The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy,resulting in an improved insulating properties of the BST film.Dielectric tunability,loss,and leakage current(LC)of the undoped and BMN doped BST thin flms were studied.The BMN dopant has remarkably reduced the dielectric loss(~38%)with no significant effect on the tunability of the BST film,leading to an increase in figure of merit(FOM).This is attributed to the opposing behavior of large Mg2+whose detrimental effect on tunability is partially compensated by small Nb5+as the two substitute Ti4+in the BST.The coupling between Mg″_(Ti)and V_(o)charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions.The LC of the films was investigated in the temperature range of 300-450K.A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from Mg″_(Ti),V_(o)and Nb_(Ti) charged defects.The carrier transport properties of the films were analyzed in light of Schottky thermionic emission(SE)and Poole-Frenkel(PF)enmission mechanisms.The result indicated that while the carrier transport mechanism in the undoped film is interface limited(SE),the conduction in the BMN doped film was dominated by bulk processes(PF).The change of the conduction mechanism from SE to PF as a result of BMN doping is atributed to the presence of uncoupled Nb_(Ti) stting as a positive trap center at the shallow donor level of the BST.展开更多
Defect engineering has been applied to prepare materials with modifiable dielectric properties.SrTiNbxO3(x=0,0.003,0.006,0.009,0.012)ceramics were synthesized using the traditional solid-state reaction method and sint...Defect engineering has been applied to prepare materials with modifiable dielectric properties.SrTiNbxO3(x=0,0.003,0.006,0.009,0.012)ceramics were synthesized using the traditional solid-state reaction method and sintered in a reducing atmosphere.All samples show excellent dielectric properties with giant permittivity(>3.5×10^(4))and low dielectric loss(<0.01).SrTiNb0.003O3 ceramic exhibits a colossal permittivity of 4.6×10^(4)and an ultralow dielectric loss of 0.005(1 kHz,room temperature)as well as great temperature stability in the range of(−60)–160℃.The mechanism of the presented colossal permittivity(CP)properties is investigated by conducting X-ray photoelectron spectroscopy(XPS)and analyzing activation energies.The results indicate that the introduction of Nb5+and the reducing sintering atmosphere together generated the formation of Ti^(3+)and V_(O)^(**).These defects further form Ti-V_(O)^(**)-Ti'_(Ti)defect dipoles,contributing to the coexisting giant permittivity and low dielectric loss in Nb-doped SrTiO_(3)(STN)ceramics.展开更多
基金National Natural Science Foundation of China(U2241242)National Key R&D Program of China(2023YFB3812000,2021YFA0716502)。
文摘The accepted doping ion in Ti^(4+)-site of PbZr_(y)Ti_(1–y)O_(3)(PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor(Q_(m)),since the acceptor coupled by oxygen vacancy becomes defect dipole,which prevents the domain rotation.In this field,a serious problem is that generally,Qm decreases as the temperature(T)increases,since the oxygen vacancies are decoupled from the defect dipoles.In this work,Q_(m) of Pb_(0.95)Sr_(0.05)(Zr_(0.53)Ti_(0.47))O_(3)(PSZT)ceramics doped by 0.40%Fe_(2)O_(3)(in mole)abnormally increases as T increases,of which the Qm and piezoelectric coefficient(d_(33))at room temperature and Curie temperature(TC)are 507,292 pC/N,and 345℃,respectively.The maximum Qm of 824 was achieved in the range of 120–160℃,which is 62.52%higher than that at room temperature,while the dynamic piezoelectric constant(d_(31))was just slightly decreased by 3.85%.X-ray diffraction(XRD)and piezoresponse force microscopy results show that the interplanar spacing and the fine domains form as temperature increases,and the thermally stimulated depolarization current shows that the defect dipoles are stable even the temperature up to 240℃.It can be deduced that the aggregation of oxygen vacancies near the fine domains and defect dipole can be stable up to 240℃,which pins domain rotation,resulting in the enhanced Q_(m) with the increasing temperature.These results give a potential path to design high Q_(m) at high temperature.
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Project supported by the fund of the Major Science and Technology Programs of Yunnan Province(202102AB080008)the Science and Technology Program of Yunnan Precious Metal Laboratory(YPML-2022050205,YPML-2022050219)。
文摘A series of Sr_(1-1.5x)Lu_(x)TiO_(3)(x=0,0.005,0.01,0.015,and 0.02)ceramics was sintered under an air at-mosphere through the solid-state reaction method.The results show that doping with Lu^(3+)consid-erably enhances material permittivity.The ceramic with x=0.01 exhibits a colossal permittivity(CP)of~101000 with a tanδof~0.16 at a frequency of 1 kHz,demonstrating enhanced stability over a wide temperature(30-300℃)and frequency(102-106 Hz)range.Based on the analysis of dielectric relaxation,X-ray photoelectron spectroscopy(XPS),and the universal dielectric response law,the CP effect is primarily due to the formation of defect dipoles,which are correlated with the presence of oxygen vacancies,such as Ti^(3+)-V_(O)^(¨)-Ti^(3+),V_(Sr)″-V_(O)^(¨),LuTi′-V_(O)^(¨)-Ti^(3+),and Lu_(Sr)·-Lu_(Ti)′-V_(O)^(¨)-Ti^(3+).These defect dipoles serve to pin electrons,limiting long-range transitions,and enhancing local po-larization.Doping with Lu^(3+)also induces a secondary Lu_(2)Ti_(2)O_(7)phase,which was characterized by X-ray diffraction(XRD)and energy-dispersive X-ray spectroscopy(EDS).The results generated in this study can inform the development and application of new CP materials based on SrTiO_(3).
基金This work was financially supported by the Natural Science Foundation of Heilongjiang Province(No.LH2021A012).
文摘PbTiO_(3)-based piezoelectric ceramics are key materials for developing various electromechanical transduc-ers.For high-power ultrasonic transducers,piezoelectric ceramics are required to possess large piezo-electric coefficient(d_(33))and high mechanical quality factor(Q_(m)).Although acceptor dopants can im-prove Q_(m),they also deteriorate d_(33).If suitable piezoelectricity-beneficial donor dopants can be intro-duced into acceptor-doped ceramics,it is very possible to obtain large d_(33)and high Q_(m)simultaneously in donor and acceptor co-doped ceramics.In this work,a series of x mol%Sm and y mol%Mn co-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-30PbTiO_(3)(PMN-30PT:x Sm,y Mn)ceramics were prepared by the solid-phase sintered method.The crystal structure,local domain structure and electromechanical properties were sys-tematically analyzed.Optimal performances were obtained in PMN-30PT:2.5Sm,1-2Mn ceramics with d_(33)=860-543 pC/N,Q_(m)=495-754,and dielectric loss tanδ=0.0055-0.0086.This high performance origi-nates from the combined effects of(Mn″Ti−V_(o)^(••))^(×)defect dipoles and the local structural heterogeneity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51562014,51262009,and 51602135)
文摘Inter-growth bismuth layer-structured ferroelectrics（BLSFs）, Bi_4Ti_3O_（12）-Na_（0.5）Bi_（4.5）Ti_4O_（15）（BIT-NBT）, were successfully synthesized using the traditional solid-state reaction method. X-ray diffraction（XRD） Rietveld refinements were conducted using GSAS software. Good agreement and low residual are obtained. The XRD diffraction peaks can be well indexed into I2 cm space group. The inter-growth structure was further observed in the high-resolution TEM image. Dielectric and impedance properties were measured and systematically analyzed. At the temperature range 763-923 K（below T_c）, doubly ionized oxygen vacancies（OVs） are localized and the short-range hopping leads to the relaxation processes with an activation energy of 0.79-1.01 eV. Above T_c, the doubly charged OVs are delocalized and become free ones, which contribute to the long-range dc conduction. The reduction in relaxation species gives rise to a higher relaxation activation energy ~ 1.6 eV.
基金supported by the Natural Science Foundation of Hebei province(E2020201021 and E2023201019)Hebei Province Innovation Capability Enhancement Plan Project(22567620H)+2 种基金Industry-University-Research Cooperation Project of Colleges and Universities in Hebei Province(CXZX2025016)Industry-University-Research Cooperation Major Projects of Shijiazhuang City(241130477A)Research Innovation Team of College of Chemistry and Environmental Science of Hebei University(hxkytd2102).
文摘The poor temperature stability of the BaTiO_(3) ceramic has always been the main problem limiting their application.This situation has been improved but sacrifices the intrinsic polarization,which significantly reduces the dielectric constant.In this work,the mechanism of multiple polarization was creatively introduced,and the temperature stability and dielectric properties of BaTiO_(3)-based ceramics are simultaneously enhanced.In particular,the Ba_(0.9925)Bi_(0.005)Ti_(0.995)Ca_(0.005)O_(2.995)(BBTC0.5)ceramic sample achieved excellent temperature stability(-14.8%to 8.85%)over an ultra-wide temperature range(-47 to 400℃)and exhibited colossal permittivity(27,125,25℃,1 kHz)and low dielectric loss(0.07,25℃,1 kHz).The dielectric properties,complex impedance spectra combined with XPS results indicate that the defective dipole clusters(Ti^(3+)-V_(O)-Ti^(3+),Bi_(Ba) and Ca″_(Ti)-V_(O))along with surface effects lead to colossal permittivity effect.More importantly,SEM images show the presence of the second phase at grain boundaries,which prevent the carriers within the grains from accumulating at the grain boundaries.As a result,the dielectric loss was reduced and the temperature stability was further extended.This strategy breaks the traditional limitation of single/noncomprehensive enhancement by singlepolarization mechanism,and is of great theoretical and practical significance to promote the research and application of high-performance BaTiO_(3)-based ceramic materials.
基金the National Natural Science Foundation of China(Grant No.52372100)the National Key Research and Development Program of China(Grant No.2019YFA0307900).
文摘Antiferroelectric materials represented by PbZrO_(3)(PZO)have excellent energy storage performance and are expected to be candidates for dielectric capacitors.It remains a challenge to further enhance the effective energy storage density and efficiency of PZO-based antiferroelectricfilms through domain engineering.In this work,the effects of three variables,misfit strain between the thinfilm and substrate,defect dipoles doping,andfilm thickness,on the domain structure and energy storage performance of PZO-based antiferroelectric materials are comprehensively investigated via phase-field simulations.The results show that applying tensile strain to thefilms can effectively increase the transition electricfield from antiferroelectric to ferroelectric.In addition,the introduction of defect dipoles while applying tensile strain can significantly reduce the hysteresis and improve energy storage efficiency.Ultimately,a recoverable energy density of 38.3 J/cm^(3)and an energy storage efficiency of about 89.4%can be realized at 1.5%tensile strain and 2%defect dipole concentration.Our work provides a new idea for the preparation of antiferroelectric thinfilms with high energy storage density and efficiency by domain engineering modulation.
基金supported by the Sichuan Science and Technology Program(No.2023NSFSC0975)National Natural Science Foundation of China(Nos.52302134 and 52302135)+1 种基金Scientific Research Foundation of Chengdu University of Information Technology(No.KYTZ202246)open research fund of the Sichuan Province Key Laboratory of Information Materials and Devices Application(No.2023XXCL003).
文摘Electrocaloric(EC)refrigeration,which employs ferroelectric(FE)ceramics as a working medium,is regarded as a promising green refrigeration technology that could potentially replace vapor-compression refrigeration.One of the principal considerations in EC application is the capacity to attain high EC strength near room temperature.In this work,we investigated the EC effect in Sm/Mn co-doped BaTiO_(3)[(Ba_(1-1.5x)Sm_(x))(Ti_(0.99)Mn_(0.01))O_(3)]ceramics.As the smallest trivalent ion that can totally occupy the A site,Sm^(3+)is not only capable of shifting the Curie temperature but also of optimizing the EC effect.Furthermore,the introduction of the Mn element into the matrix results in the formation of defect dipoles,which also serves to enhance the EC performance.Therefore,large EC strengths of △T/△E=0.49Kmm kV^(-1)(@51℃),0.34Kmm kV^(-1)(@39℃)and 0.21Kmm kV^(-1)(@30℃)were,respectively,achieved in x=0.05-0.07 ceramics,demonstrating the potential for future refrigeration applications.
基金This work was supported by Key Research and Development Program of Ministry of Science and Technology of China(No.2022YFB3204000).
文摘Piezoelectric PZT ceramics with high piezoelectric properties and good thermal stability are urgently desired concerning the practical application.New compositions of LiNbO_(3) modified Pb(Ni_(1/3)Nb_(2/3))O_(3)single bondPbZrO_(3)single bondPbTiO_(3) ceramics have been prepared in this study.The effects of the introduction of the LiNbO_(3) on the system were comprehensively investigated in terms of the phase structure,microstructure,electric properties,and thermal stability behavior of the ceramics.All compositions are located in the morphotropic phase boundary(MPB)region,and the ratio of the rhombohedral(R)phase increases obviously with the increase of LiNbO_(3) concentration.With increasing the LiNbO_(3) content,the piezoelectric properties were significantly enhanced.The sample added with 2%(in mole)LiNbO_(3) shows excellent electric properties,including T_(m)=185℃,εr=5,643,k_(p)=0.626,Q_(m)=51,d_(33)=902 pC/N.More importantly,no thermal depolarization behavior was observed in the temperature range of 25–100℃.For PNN-PZT-x%LN ceramics,which is mainly attributed to the pinning effect resulted by the(Li_(Pb)-Nb_(Zr/Ti)) defect dipoles.
基金This work was funded by the National Natural Science Foundation of China(Grant Nos.11702037 and 11832007)State Key Laboratory of Mechanics and Control of Mechanical Structures,Nanjing University of Aeronautics and astronautics(Grant No.MCMS-E-0522G01)+1 种基金the Open Foundation of Guangdong Provincial Key Laboratory of Materials and Technologies for Energy Conversion(Grant No.MATEC2022KF001)as well as the Cultivation Project for the Natural Science Foundation and Highlevel Talent at Chengdu University(Grant No.Z1350).
文摘High-performance Pb(Zr_(1−x)Ti_(x))O_(3)(PZT)piezoceramics are urgently desired by the market in view of their expanded operating temperature range,reduced property temperature dependence,and enhanced sensitivity and acoustic power.In this work,we reported a kind of low-cost and high-performance 0.06BiYbO_(3)–0.94Pb(Zr_(0.48)Ti_(0.52))O_(3) ternary piezoceramics;the modifying effects of La_(2)O_(3) on this perovskite system were investigated in terms of the structures,electrical properties,and thermal depolarization behaviors of ceramics.The field-dependent dielectric and conduction properties indicated that there are close correlations among oxygen vacancies(VO),conducting electrons,and intrinsic conduction process.The degradation in ferroelectric properties observed in those samples doped with more than 0.15 wt%of La_(2)O_(3) indicated that the occupying mechanisms of La^(3+)changed from the donor substitution for Pb^(2+)to the isovalent substitution for Bi^(3+).The thermally depoling micromechanisms of ceramics were revealed from the thermodynamic processes of defect dipoles and intrinsic dipoles within ferroelectric domains.The sample doped with 0.15 wt%of La_(2)O_(3) shows excellent electrical properties with TC=387℃,d33=332 pC/N,TKε=5.81×10^(−3)℃−1,Pr=20.66μC/cm^(2),Td=356℃.The significantly enhanced electrical properties and thermal depolarization temperature benefited from the donor substitution of La3+,decreasing the oxygen vacancy concentration in the lattice and possibly optimizing the ferroelectric domain structure of ceramics.
基金This publication is based on research sponsored by the Defense Microelectronics Activity(DMEA)under agreement number H94003-11-2-1103.
文摘Ba(Mg_(1/3)Nb_(2/3))O_(3)(BMN)doped and undoped B_(0.45)Sr_(0.55)TiO_(3)(BST)thin films were deposited via radio frequency magnetron sputtering on PUTiO_(2)/SiO_(2)/Al_(2)O_(3) substrates.The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy,resulting in an improved insulating properties of the BST film.Dielectric tunability,loss,and leakage current(LC)of the undoped and BMN doped BST thin flms were studied.The BMN dopant has remarkably reduced the dielectric loss(~38%)with no significant effect on the tunability of the BST film,leading to an increase in figure of merit(FOM).This is attributed to the opposing behavior of large Mg2+whose detrimental effect on tunability is partially compensated by small Nb5+as the two substitute Ti4+in the BST.The coupling between Mg″_(Ti)and V_(o)charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions.The LC of the films was investigated in the temperature range of 300-450K.A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from Mg″_(Ti),V_(o)and Nb_(Ti) charged defects.The carrier transport properties of the films were analyzed in light of Schottky thermionic emission(SE)and Poole-Frenkel(PF)enmission mechanisms.The result indicated that while the carrier transport mechanism in the undoped film is interface limited(SE),the conduction in the BMN doped film was dominated by bulk processes(PF).The change of the conduction mechanism from SE to PF as a result of BMN doping is atributed to the presence of uncoupled Nb_(Ti) stting as a positive trap center at the shallow donor level of the BST.
基金This work was supported by the National Key R&D Program of China(Grant No.2021YFB3800601)the Basic Science Center Project of the National Natural Science Foundation of China(Grant No.52388201).
文摘Defect engineering has been applied to prepare materials with modifiable dielectric properties.SrTiNbxO3(x=0,0.003,0.006,0.009,0.012)ceramics were synthesized using the traditional solid-state reaction method and sintered in a reducing atmosphere.All samples show excellent dielectric properties with giant permittivity(>3.5×10^(4))and low dielectric loss(<0.01).SrTiNb0.003O3 ceramic exhibits a colossal permittivity of 4.6×10^(4)and an ultralow dielectric loss of 0.005(1 kHz,room temperature)as well as great temperature stability in the range of(−60)–160℃.The mechanism of the presented colossal permittivity(CP)properties is investigated by conducting X-ray photoelectron spectroscopy(XPS)and analyzing activation energies.The results indicate that the introduction of Nb5+and the reducing sintering atmosphere together generated the formation of Ti^(3+)and V_(O)^(**).These defects further form Ti-V_(O)^(**)-Ti'_(Ti)defect dipoles,contributing to the coexisting giant permittivity and low dielectric loss in Nb-doped SrTiO_(3)(STN)ceramics.
