采用固相反应法制备了Ca_(0.94)Ce_(0.06)Bi_(4)Ti_(4-x)Nb_(x)O_(15)(CCBTN)铋层状高温压电陶瓷,研究了B位Nb掺杂对陶瓷晶体结构、微观形貌、介电、压电性能的影响规律。结果表明:制备的CCBTN陶瓷均具有单一的铋层状结构相,少量Nb掺杂...采用固相反应法制备了Ca_(0.94)Ce_(0.06)Bi_(4)Ti_(4-x)Nb_(x)O_(15)(CCBTN)铋层状高温压电陶瓷,研究了B位Nb掺杂对陶瓷晶体结构、微观形貌、介电、压电性能的影响规律。结果表明:制备的CCBTN陶瓷均具有单一的铋层状结构相,少量Nb掺杂有利于陶瓷压电常数及热稳定性能的提升。当Nb掺杂量x=0.06时,陶瓷具有最高的压电常数(d33=19.2pC·N^(-1)),是纯CBT陶瓷压电常数(d33=8 p C·N^(-1))的2.4倍,且退火至500℃时其压电常数仍保持室温值的90%以上,表现出较优异的热稳定性。同时,该陶瓷具有高的居里温度(Tc=769℃)、低的介电损耗(tanδ=0.65%)及高的电阻率(ρdc=2.0×10^(7)Ω·cm@500℃),是高温压电传感器制作的优异候选材料。展开更多
通过传统固相法合成了具有超晶格结构的Ba Bi_(8)Ti_(7-x)(Cu_(1/3)Nb_(2/3))_(x)O_(27)(简称:BBT-BIT-x(Cu_(1/3)Nb_(2/3))共生陶瓷。结果表明,BBT-BIT-x(Cu_(1/3)Nb_(2/3))陶瓷的电学性能得到了有效地改善:随着x的增加,介电损耗呈现...通过传统固相法合成了具有超晶格结构的Ba Bi_(8)Ti_(7-x)(Cu_(1/3)Nb_(2/3))_(x)O_(27)(简称:BBT-BIT-x(Cu_(1/3)Nb_(2/3))共生陶瓷。结果表明,BBT-BIT-x(Cu_(1/3)Nb_(2/3))陶瓷的电学性能得到了有效地改善:随着x的增加,介电损耗呈现先减小后增大的趋势,居里温度逐渐增加(Tc:483~494℃);压电常数和剩余极化强度都呈现出先增大后减小的趋势,其中x=0.035时压电常数和剩余极化强度同时达到最高值分别为d_(33)=18 p C/N,2P_(r)=16.5μC/cm^(2)。此外,BBT-BIT-0.035(Cu_(1/3)Nb_(2/3))陶瓷具有良好的热稳定性,在400℃/0.5 h下压电常数仍有14 p C/N,是起始值的82.4%,这有利于在较高温度的环境下工作。展开更多
We present an efficient strategy,that is the co-substitution of Fe^(3+)and Ta^(5+)ions with large radius for Ti^(4+)ion,to enhance energy storage performance of Ba_(2)Bi_(4)Ti_(5)O_(18) film.For the films co-doped wit...We present an efficient strategy,that is the co-substitution of Fe^(3+)and Ta^(5+)ions with large radius for Ti^(4+)ion,to enhance energy storage performance of Ba_(2)Bi_(4)Ti_(5)O_(18) film.For the films co-doped with Fe^(3+)and Ta^(5+)ions,the maximum polarization under the same external electric field is improved because the radius of Fe^(3+)and Ta^(5+)ions is larger than that of Ti^(4+)ion.Moreover,due to the composition and chemical disorder,the relaxor properties are also slightly improved,which can not be achieved by the film doped with Fe^(3+)ions only.What is more,for the films doped with Fe^(3+)ion only,the leakage current density increases greatly due to the charge imbalance,resulting in a significant decrease in breakdown strength.It is worth mentioning that the breakdown strength of Fe^(3+)and Ta^(5+)ions co-doped film does not decrease due to the charge balance.Another important point is the recoverable energy storage density of the films co-doped with Fe^(3+)and Ta^(5+)ions has been greatly improved based on the fact that the maximum external electric field does not decrease and the maximum polarization under the same external electric field increases.On top of that,the hysteresis of the polarization has also been improved.Finally,the co-doped films with Fe^(3+)and Ta^(5+)ions have good frequency and temperature stability.展开更多
Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films have important application values in the fields of 5G communication technology,wearable electronic devices and artifici...Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films have important application values in the fields of 5G communication technology,wearable electronic devices and artificial intelligence.In this work,Fe_(3)O_(4)/polyamic acid(PAA)nanofiber films are prepared by in-situ polymerization and electrospinning technology,and Ti_(3)C_(2)T_(x)nanosheets are deposited on the surface of the Fe_(3)O_(4)/PAA nanofiber films via vacuum-assisted filtration.Then,Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/polyimide(PI))composite films are obtained by thermal imidization.The two sides of the Janus films exhibit completely different properties.The Fe_(3)O_(4)/PI side has excellent hydrophobicity and insulation property,and the Ti_(3)C_(2)T_(x)side has hydrophilicity and terrific conductivity.When the mass fraction of Ti_(3)C_(2)T_(x)is 80 wt.%,the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite film has excellent EMI shielding performances and mechanical properties,with EMI shielding effectiveness,tensile strength and Young’s modulus reaching 66 dB,114.5 MPa and 5.8 GPa,respectively.At the same time,electromagnetic waves show different absorption shielding effectiveness(SEA)when incident from two sides of the Janus films.When the electromagnetic waves are incident from the Fe_(3)O_(4)/PI side,the SEA of the Janus film is 58 dB,much higher than that when the electromagnetic waves are incident from the Ti_(3)C_(2)T_(x)side(39 dB).In addition,the Ti_(3)C_(2)T_(x)side of the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite films also has excellent electrothermal and photothermal conversion performances.When the applied voltage is 4 V,the stable surface temperature reaches 108°C;when it is irradiated by simulated sunlight with power density of 200 mW/cm2,the stable surface temperature reaches 95℃.展开更多
Bismuth layer-structured ferroelectric ceramics of Na0.5Bi4.5-x(Nd_(0.5)Ce_(0.5)))xTi4O15(NBT-x,0.0≤x≤0.4)were synthesized by a traditional solid-state reaction.The effect of(Nd,Ce)substitution for A-site on the mic...Bismuth layer-structured ferroelectric ceramics of Na0.5Bi4.5-x(Nd_(0.5)Ce_(0.5)))xTi4O15(NBT-x,0.0≤x≤0.4)were synthesized by a traditional solid-state reaction.The effect of(Nd,Ce)substitution for A-site on the microstructure and electrical properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)(NBT)-based piezoelectric ceramics was investigated.X-ray diffraction(XRD)analysis revealed that the(Nd,Ce)-modified NBT ceramics have a pure four-layer Aurivillius type structure.The piezoelectric properties of NBT ceramics were significantly improved by the modification of neodymium and cerium.The Curie temperature TC gradually decreased from 638℃to 618℃with increasing the(Nd,Ce)modification.The piezoelectric constant d33,mechanical quality factor Qm,dielectric loss tanδand Curie temperature TC of the Na0.5Bi4.3(Nd_(0.5)Ce_(0.5)))0.2Ti4O15 ceramic were found to be 28 pC/N,3239,0.0032 and 630℃,respectively.Thermal annealing studies indicated that the(Nd,Ce)-modified NBT ceramics possess stable piezoelectric properties,demonstrating that the Na0.5Bi4.3(Nd_(0.5)Ce_(0.5)))0.2Ti4O15 ceramic is a promising candidate for high temperature applications.展开更多
Aurivillius Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and Bi_(4)Ti_(3)O_(12)compounds were synthesized via solid-state reaction technique.X-ray powder diffraction study confirmed monophasic four-layered Na_(0.5)Bi_(4.5)Ti_(4)O_(15...Aurivillius Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and Bi_(4)Ti_(3)O_(12)compounds were synthesized via solid-state reaction technique.X-ray powder diffraction study confirmed monophasic four-layered Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and three-layered Bi_(4)Ti_(3)O_(12) ceramics.Dielectric relaxation and conduction behaviors of Na-contained Na_(0.5)Bi_(4.5)Ti_(4)O_(15)ceramics were thoroughly investigated in a large scale of temperature of 30-650℃ and frequency of 40 Hz^(-1) MHz.In addition,comparative studies of both the compounds were discussed.Impedance and modulus analyses revealed a single relaxation behavior in Na_(0.5)Bi_(4.5)Ti_(4)O_(15) compound which was originated from the grain’s interior with grain resistance of 2.189×10^(5)Ω and capacitance of 4.268×10^(-10) F at 570℃.While in Bi_(4)Ti_(3)O_(12) ceramic the relaxation was due to the contributions of grain and grain boundaries.Alternating current(AC)conductivity analysis revealed the presence of two different conduction regions in both the compounds.Activation energies for the two different conduction mechanisms,i.e.,in low-temperature region and in high-temperature region were calculated to be~0.23 and~1.27 eV at 1 kHz for Na_(0.5)Bi_(4.5)Ti_(4)O_(15) compound and~0.43 eV and~0.97 eV at 1 kHz for Bi_(4)Ti_(3)O_(12) compound,respectively.The present study of dielectric relaxation and conduction behaviors would be helpful for further investigations of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)-related Aurivillius compounds.展开更多
As one of the representatives of lead-free NBT ceramics,Na_(0.5)Bi_(4.5)Ti_(4)O_(15) has still attracted much attention due to its excellent dielectric properties and has become the focus of research.However,its piezo...As one of the representatives of lead-free NBT ceramics,Na_(0.5)Bi_(4.5)Ti_(4)O_(15) has still attracted much attention due to its excellent dielectric properties and has become the focus of research.However,its piezoelectric properties are far from satisfactory.In order to improve the piezoelectric properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15),Na_(0.5)Bi_(4.5)Ti_(4-x)Mg_(x)O_(y)–BaTiO_(3)(NBTM–BT)composite ceramics were synthesized by a conventional mixed oxide route and sintered at 1040℃ through two-step method.We optimized the electrical properties of NBTM–BT by changing the stoichiometric ratio of Mg content and studied its microscopic mechanism.The piezoelectric coefficient(d33)is stable at about 20 pC/N.Moreover,the maximum remanent polarization(2Pr)of the ceramic is 3.08C/cm^(2) with the coercive field of 18.01 kV/cm.The dielectric constant and dielectric loss for Na_(0.5)Bi_(4.5)Ti_(3.96)Mg_(0.04)–BT composite ceramic were found to be 486 and 0.17 at 10 kHz,respectively.The characteristic peaks of BT and Na_(0.5)Bi_(4.5)Ti_(4)O_(15) can be observed clearly from the X-ray diffraction analysis.SEM analysis showed that all samples were well crystallized.Consequently,the piezoelectric and ferroelectric properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)–BT composite ceramic will be enhanced much by Mg doping,which means it has a wider range of applications in electronic devices such as piezoelectric devices.展开更多
文摘采用固相反应法制备了Ca_(0.94)Ce_(0.06)Bi_(4)Ti_(4-x)Nb_(x)O_(15)(CCBTN)铋层状高温压电陶瓷,研究了B位Nb掺杂对陶瓷晶体结构、微观形貌、介电、压电性能的影响规律。结果表明:制备的CCBTN陶瓷均具有单一的铋层状结构相,少量Nb掺杂有利于陶瓷压电常数及热稳定性能的提升。当Nb掺杂量x=0.06时,陶瓷具有最高的压电常数(d33=19.2pC·N^(-1)),是纯CBT陶瓷压电常数(d33=8 p C·N^(-1))的2.4倍,且退火至500℃时其压电常数仍保持室温值的90%以上,表现出较优异的热稳定性。同时,该陶瓷具有高的居里温度(Tc=769℃)、低的介电损耗(tanδ=0.65%)及高的电阻率(ρdc=2.0×10^(7)Ω·cm@500℃),是高温压电传感器制作的优异候选材料。
文摘在LiNO_3/SiO_2/Si基板上制备了Li_(1-x)Bi_(4+x)Ti_4O_(15)系列薄膜(x=0.3、0.4、0.5、0.6),并系统分析了这些薄膜的微观结构以及铁电、介电及漏电等电学特性。研究结果表明,在氮气气氛中以600℃持温30 min制备的单一相薄膜中Li0.5Bi4.5Ti4O15薄膜的结晶效果最好,且在其表面可成长出独立晶粒分布状态;x为0.5时薄膜的剩余极化强度2Pr=53.5μC/cm2、矫顽场2Ec=144.2 k V/cm,此时薄膜的铁电性能相对最佳;该系列薄膜的介电常数介于37~100,介电损失相对偏高,介于0.7~1.0;所有薄膜的漏电流均随外加电压的增加而逐渐增大,其中Li0.5Bi4.5Ti4O15薄膜漏电流最小,外加电压为10 V时其值约为3.88×10-6A。
文摘通过传统固相法合成了具有超晶格结构的Ba Bi_(8)Ti_(7-x)(Cu_(1/3)Nb_(2/3))_(x)O_(27)(简称:BBT-BIT-x(Cu_(1/3)Nb_(2/3))共生陶瓷。结果表明,BBT-BIT-x(Cu_(1/3)Nb_(2/3))陶瓷的电学性能得到了有效地改善:随着x的增加,介电损耗呈现先减小后增大的趋势,居里温度逐渐增加(Tc:483~494℃);压电常数和剩余极化强度都呈现出先增大后减小的趋势,其中x=0.035时压电常数和剩余极化强度同时达到最高值分别为d_(33)=18 p C/N,2P_(r)=16.5μC/cm^(2)。此外,BBT-BIT-0.035(Cu_(1/3)Nb_(2/3))陶瓷具有良好的热稳定性,在400℃/0.5 h下压电常数仍有14 p C/N,是起始值的82.4%,这有利于在较高温度的环境下工作。
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.12074204,11864028,and 11904054)the Natural Science Foundation of Inner Mongolia,China(Grant No.2022ZD06).
文摘We present an efficient strategy,that is the co-substitution of Fe^(3+)and Ta^(5+)ions with large radius for Ti^(4+)ion,to enhance energy storage performance of Ba_(2)Bi_(4)Ti_(5)O_(18) film.For the films co-doped with Fe^(3+)and Ta^(5+)ions,the maximum polarization under the same external electric field is improved because the radius of Fe^(3+)and Ta^(5+)ions is larger than that of Ti^(4+)ion.Moreover,due to the composition and chemical disorder,the relaxor properties are also slightly improved,which can not be achieved by the film doped with Fe^(3+)ions only.What is more,for the films doped with Fe^(3+)ion only,the leakage current density increases greatly due to the charge imbalance,resulting in a significant decrease in breakdown strength.It is worth mentioning that the breakdown strength of Fe^(3+)and Ta^(5+)ions co-doped film does not decrease due to the charge balance.Another important point is the recoverable energy storage density of the films co-doped with Fe^(3+)and Ta^(5+)ions has been greatly improved based on the fact that the maximum external electric field does not decrease and the maximum polarization under the same external electric field increases.On top of that,the hysteresis of the polarization has also been improved.Finally,the co-doped films with Fe^(3+)and Ta^(5+)ions have good frequency and temperature stability.
基金supports from the National Natural Science Foundation of China(Nos.U21A2093 and 51903145)Fundamental Research Funds for the Central Universities(No.D5000210627)+1 种基金Y.L.Z.would like to thank the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX2021107)This work is also financially supported by Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films have important application values in the fields of 5G communication technology,wearable electronic devices and artificial intelligence.In this work,Fe_(3)O_(4)/polyamic acid(PAA)nanofiber films are prepared by in-situ polymerization and electrospinning technology,and Ti_(3)C_(2)T_(x)nanosheets are deposited on the surface of the Fe_(3)O_(4)/PAA nanofiber films via vacuum-assisted filtration.Then,Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/polyimide(PI))composite films are obtained by thermal imidization.The two sides of the Janus films exhibit completely different properties.The Fe_(3)O_(4)/PI side has excellent hydrophobicity and insulation property,and the Ti_(3)C_(2)T_(x)side has hydrophilicity and terrific conductivity.When the mass fraction of Ti_(3)C_(2)T_(x)is 80 wt.%,the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite film has excellent EMI shielding performances and mechanical properties,with EMI shielding effectiveness,tensile strength and Young’s modulus reaching 66 dB,114.5 MPa and 5.8 GPa,respectively.At the same time,electromagnetic waves show different absorption shielding effectiveness(SEA)when incident from two sides of the Janus films.When the electromagnetic waves are incident from the Fe_(3)O_(4)/PI side,the SEA of the Janus film is 58 dB,much higher than that when the electromagnetic waves are incident from the Ti_(3)C_(2)T_(x)side(39 dB).In addition,the Ti_(3)C_(2)T_(x)side of the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite films also has excellent electrothermal and photothermal conversion performances.When the applied voltage is 4 V,the stable surface temperature reaches 108°C;when it is irradiated by simulated sunlight with power density of 200 mW/cm2,the stable surface temperature reaches 95℃.
基金supported by the National Natural Science Foundation of China(No.51262009)Natural Science Foundation of Jiangxi(Nos.20132BAB202002,20122BAB202001 and 20122BAB203019)+1 种基金Foundation of Training Academic and Technical Leaders for Main Majors of Jiangxi(No.2010DD00800)Colleges and Universities“Advanced Ceramics”Scientific and Technological Innovation Team of Jiangxi,and Foundation of Jiangxi Provincial Department of Education(Nos.GJJ3629 and GJJ3630).
文摘Bismuth layer-structured ferroelectric ceramics of Na0.5Bi4.5-x(Nd_(0.5)Ce_(0.5)))xTi4O15(NBT-x,0.0≤x≤0.4)were synthesized by a traditional solid-state reaction.The effect of(Nd,Ce)substitution for A-site on the microstructure and electrical properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)(NBT)-based piezoelectric ceramics was investigated.X-ray diffraction(XRD)analysis revealed that the(Nd,Ce)-modified NBT ceramics have a pure four-layer Aurivillius type structure.The piezoelectric properties of NBT ceramics were significantly improved by the modification of neodymium and cerium.The Curie temperature TC gradually decreased from 638℃to 618℃with increasing the(Nd,Ce)modification.The piezoelectric constant d33,mechanical quality factor Qm,dielectric loss tanδand Curie temperature TC of the Na0.5Bi4.3(Nd_(0.5)Ce_(0.5)))0.2Ti4O15 ceramic were found to be 28 pC/N,3239,0.0032 and 630℃,respectively.Thermal annealing studies indicated that the(Nd,Ce)-modified NBT ceramics possess stable piezoelectric properties,demonstrating that the Na0.5Bi4.3(Nd_(0.5)Ce_(0.5)))0.2Ti4O15 ceramic is a promising candidate for high temperature applications.
基金financially supported by National Natural Science Foundation of China(Nos.51972029 and 51772029)。
文摘Aurivillius Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and Bi_(4)Ti_(3)O_(12)compounds were synthesized via solid-state reaction technique.X-ray powder diffraction study confirmed monophasic four-layered Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and three-layered Bi_(4)Ti_(3)O_(12) ceramics.Dielectric relaxation and conduction behaviors of Na-contained Na_(0.5)Bi_(4.5)Ti_(4)O_(15)ceramics were thoroughly investigated in a large scale of temperature of 30-650℃ and frequency of 40 Hz^(-1) MHz.In addition,comparative studies of both the compounds were discussed.Impedance and modulus analyses revealed a single relaxation behavior in Na_(0.5)Bi_(4.5)Ti_(4)O_(15) compound which was originated from the grain’s interior with grain resistance of 2.189×10^(5)Ω and capacitance of 4.268×10^(-10) F at 570℃.While in Bi_(4)Ti_(3)O_(12) ceramic the relaxation was due to the contributions of grain and grain boundaries.Alternating current(AC)conductivity analysis revealed the presence of two different conduction regions in both the compounds.Activation energies for the two different conduction mechanisms,i.e.,in low-temperature region and in high-temperature region were calculated to be~0.23 and~1.27 eV at 1 kHz for Na_(0.5)Bi_(4.5)Ti_(4)O_(15) compound and~0.43 eV and~0.97 eV at 1 kHz for Bi_(4)Ti_(3)O_(12) compound,respectively.The present study of dielectric relaxation and conduction behaviors would be helpful for further investigations of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)-related Aurivillius compounds.
基金We wish to thank China Scholarship Council(CSC).CSC supports us as academic visitors to join Derek C.Sinclair’s Research Group at the Department of Materials Science and Engineering, University of Sheffield, UK. We thank thefunding of Natural Science Foundation of Hubei Province,China (Grant No. 2017CFB574).
文摘As one of the representatives of lead-free NBT ceramics,Na_(0.5)Bi_(4.5)Ti_(4)O_(15) has still attracted much attention due to its excellent dielectric properties and has become the focus of research.However,its piezoelectric properties are far from satisfactory.In order to improve the piezoelectric properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15),Na_(0.5)Bi_(4.5)Ti_(4-x)Mg_(x)O_(y)–BaTiO_(3)(NBTM–BT)composite ceramics were synthesized by a conventional mixed oxide route and sintered at 1040℃ through two-step method.We optimized the electrical properties of NBTM–BT by changing the stoichiometric ratio of Mg content and studied its microscopic mechanism.The piezoelectric coefficient(d33)is stable at about 20 pC/N.Moreover,the maximum remanent polarization(2Pr)of the ceramic is 3.08C/cm^(2) with the coercive field of 18.01 kV/cm.The dielectric constant and dielectric loss for Na_(0.5)Bi_(4.5)Ti_(3.96)Mg_(0.04)–BT composite ceramic were found to be 486 and 0.17 at 10 kHz,respectively.The characteristic peaks of BT and Na_(0.5)Bi_(4.5)Ti_(4)O_(15) can be observed clearly from the X-ray diffraction analysis.SEM analysis showed that all samples were well crystallized.Consequently,the piezoelectric and ferroelectric properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)–BT composite ceramic will be enhanced much by Mg doping,which means it has a wider range of applications in electronic devices such as piezoelectric devices.