To reduce the coercive field of Na_(0.5)Bi_(0.5)TiO_(3),Ba TiO_(3)were added as dopant materials.Then the(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBaTiO_(3)ceramic samples were produced in solid synthetic way.The optimum preparat...To reduce the coercive field of Na_(0.5)Bi_(0.5)TiO_(3),Ba TiO_(3)were added as dopant materials.Then the(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBaTiO_(3)ceramic samples were produced in solid synthetic way.The optimum preparation condition and piezoelectric properties of the samples were investigated.The XRD results show that the fabric transites from rhombohedral to tetragonal gradually with the substitution of the Ba^(2+).The morphotropic phase boundaries(MPB)exists in the composition range of 0.06.展开更多
Antiferroelectric ferroelectric (AFE-FE) phase transition in ceramic Pbo.97Lao.02(Zro.75Snon36Tion14)O3 (PLZST) was studied by dielectric spectroscopy as functions of frequency (102-105 Hz) and pressure (0-50...Antiferroelectric ferroelectric (AFE-FE) phase transition in ceramic Pbo.97Lao.02(Zro.75Snon36Tion14)O3 (PLZST) was studied by dielectric spectroscopy as functions of frequency (102-105 Hz) and pressure (0-500 MPa) under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were mea- sured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant um dergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE AFE and AFE-FE.展开更多
Lead-free piezoelectric ceramics of (Bi1/2Na1/2)TiO3-BaTiO3(BNT-BT) were prepared by the conventional piezoelectric ceramic preparation technique (free air atmosphere sintering). The influence of BaTiO3 additive amoun...Lead-free piezoelectric ceramics of (Bi1/2Na1/2)TiO3-BaTiO3(BNT-BT) were prepared by the conventional piezoelectric ceramic preparation technique (free air atmosphere sintering). The influence of BaTiO3 additive amount and La2O3 additive amount on the properties of BNT-BT lead-free piezoceramics were investigated. The results show that the dielectric constant(ε) and piezoelectric strain constant(d33) of materials start increasing and then decreasing while BaTiO3 additive amount increasing, the e and d33 of materials have maximum value (ε= 1650, d33 = 120 PC·N -1 ) while x (BaTiO3) =0.06 mol. Theεand d33 of materials start increasing and then decreasing while La2O3 additive amount increasing, the e and d33 of materials have maximum value (ε= 1684, d33 = 153 PC·N-1) while w(La2O3) =0.3% . The influence of La2O3 additive amount on the microstructure of BNT-BT piezoelectric ceramics was analysed by SEM( scanning electron microscope). The influence mechanism of La2O3 additive amount on the properties of BNT-BT piezoelectric ceramics was discussed. The BNT-BT ceramics with optimum comprehensive properties were obtained.展开更多
Aim The piezoelectric properties and cytotoxicity of a porous lead-free piezoelectric ceramic for use as a direct bone substitute were investigated. Methodology Cold isostatic pressing (CIP) was applied to fabricate...Aim The piezoelectric properties and cytotoxicity of a porous lead-free piezoelectric ceramic for use as a direct bone substitute were investigated. Methodology Cold isostatic pressing (CIP) was applied to fabricate porous lithium sodium potassium niobate (Li0.06Na0.5K0.44) NbO3 specimens using a pore-forming method. The morphologies of the CIP-processed specimens were characterized and compared to those of specimens made by from conventional pressing procedures. The effects of the ceramic on the attachment and proliferation of osteoblasts isolated from the cranium of 1-day-old Sprague- Dawley rats were examined by a scanning electron microscopy (SEM) and metbylthiazol tetrazolium (MTT) assay. Results The results showed that CIP enhanced piezoelectricity and biological performance of the niobate specimen, and also promoted an extracellular matrix-like topography of it. In vitro studies showed that the CIP-enhanced material had positive effects on the attachment and proliferation of osteoblasts. Conclusion Niobate ceramic generated by CIP shows a promise for being a piezoelectric composite bone substitute.展开更多
Lead-free piezoelectric (K0.5sNa0.5)1-xLixNbO3 (x = 0at%-20at%) ceramics were synthesized by spark plasma sintering (SPS) at low temperature and the effects of LiNbO3 addition on its crystal structure and proper...Lead-free piezoelectric (K0.5sNa0.5)1-xLixNbO3 (x = 0at%-20at%) ceramics were synthesized by spark plasma sintering (SPS) at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of (K0.5Na0.5)NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the (K0.5Na0.5)1-xLixNbO3 ceramics.展开更多
CuO-doped(Ag0.75Li0.1Na0.1K0.05)NbO3(ALNKN-xCuO, x = 0.2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure...CuO-doped(Ag0.75Li0.1Na0.1K0.05)NbO3(ALNKN-xCuO, x = 0.2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2NbrO16- type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with'the grain size of about 1 ~tm was formed for the ceramics with 0.5mo1% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = lm01% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.展开更多
Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the le...Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and...展开更多
Lead-free piezoelectric NaxK1-xNbO3(x = 0.3-0.8)(NKN) ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special ...Lead-free piezoelectric NaxK1-xNbO3(x = 0.3-0.8)(NKN) ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary(MPB) in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.展开更多
Effects of A-site non-stoichiometry on the structural and electrical properties of 0.96K0.5+xNa0.5+xNbO3- 0.04LiSbO3 lead-free piezoelectric ceramics were examined for 0 ≤ x ≤0.02. The piezoelectric coefficients e...Effects of A-site non-stoichiometry on the structural and electrical properties of 0.96K0.5+xNa0.5+xNbO3- 0.04LiSbO3 lead-free piezoelectric ceramics were examined for 0 ≤ x ≤0.02. The piezoelectric coefficients exhibited a maximum, d33 = 187 pC/N at x = 0.0075, coinciding with the maximum of the grain size and the apparent density at x = 0.0075. The apparent density and the piezoelectric coefficients decreased with increasing x at higher x which was likely due to the crystal geometrical distortion of 0.96K0.5+xNa0.5+xNbO3-0.04LiSbO3. In addition, super-large grains were found and this may be due to liquid phase sintering. Excess (K++Na+) attracted a sum of space charges to keep the charge neutral, resulting in charge leakage during the course of ceramic polarization, influencing the piezoelectric and ferroelectric properties. These findings are of importance for guiding the design of Ko.sNao.sNbO3-based lead-free ceramics with enhanced electrical properties.展开更多
The microstructures and electrical properties of Bi0.5(Na1-x-yKxLiy)0.5TiO3 lead-free piezoelectric ceramics were studied.These ceramics were prepared by conventional ceramic technique.XRD analysis reveals that the ...The microstructures and electrical properties of Bi0.5(Na1-x-yKxLiy)0.5TiO3 lead-free piezoelectric ceramics were studied.These ceramics were prepared by conventional ceramic technique.XRD analysis reveals that the ceramics possess almost pure perovskite phase when y≤0.2.The SEM results show that,with more amounts of Li+,the crystalline grain growing speed is accelerated,and the sintering temperature can effectively be decreased.The measurements of piezoelectric properties indicate that the ceramics with relatively low amount of Li+ and high amount of K+ have comparatively large piezoelectricity.The dielectric measurements show that the ceramics have properties like relaxor ferroelectrics and diffuse phase transition(DPT) at Td and Tc,respectively.The results of ferroelectric measurements reveal the system has relatively higher remanent polarization Pr(27.6 μC/cm2) and lower coercive field Ec(37.5 kV/cm).展开更多
It is crucial to discover lead-free materials with ultrahigh recoverable energy density(Wrec)that can be employed in future pulse power capacitors.In this work,a high Wrec of 4.51 J/cm^(3) was successfully obtained in...It is crucial to discover lead-free materials with ultrahigh recoverable energy density(Wrec)that can be employed in future pulse power capacitors.In this work,a high Wrec of 4.51 J/cm^(3) was successfully obtained in lead-free Nd-doped AgNb_(0.8)Ta_(0.2)O_(3) antiferroelectric ceramics at an applied electric field of 290 kV/cm.It is discovered that Nd doping paired with Nb-site vacancies could stabilize the antiferroelectric phase by lowering the temperatures of the M1-M2 and M2-M3 phase transitions,which leads to higher energy storage efficiency.Furthermore,Nd and Ta co-doping will contribute to the electrical homogeneity and low electrical conductivity,resulting in large breakdown strengths.Aliovalent doping in Ag-site with Nb-site vacancies serves as a novel strategy for the construction of AgNbO_(3)-based ceramics with excellent energy storage performance.展开更多
In this work,(1−x)(0.92NaNbO_(3)-0.08BaTiO_(3))-xCa_(0.7)La_(0.2)TiO_(3)(NNBT-xCLT)ceramics were successfully designed and prepared by the solid-state reaction method.Investigations on the structure,dielectric,a...In this work,(1−x)(0.92NaNbO_(3)-0.08BaTiO_(3))-xCa_(0.7)La_(0.2)TiO_(3)(NNBT-xCLT)ceramics were successfully designed and prepared by the solid-state reaction method.Investigations on the structure,dielectric,and energy storage properties were performed.The NNBT-0.25CLT ceramic with orthorhombic phase at room temperature was found to exhibit extremely small grain size and compacted microstructure.A large Wrec of 3.1 J/cm^(3) and a highηof 91.5%under the electric field of 360 kV/cm were achieved simultaneously in the sample.In addition,the energy storage performance of the sample exhibits thermal stability over the temperature range of 25-140°C and the frequency range of 5-500 Hz.The charge and discharge tests reveal that the ceramic shows a large current density CD of 965 A/cm2 and power density PD of 154 MW/cm^(3).This work demonstrates that the NNBT-0.25CLT ceramic is a prospective energy storage material for potential application in the field of pulsed power devices.展开更多
A greater number of compact and reliable electrostatic capacitors are in demand due to the Internet of Things boom and rapidly growing complex and integrated electronic systems,continuously promoting the development o...A greater number of compact and reliable electrostatic capacitors are in demand due to the Internet of Things boom and rapidly growing complex and integrated electronic systems,continuously promoting the development of high-energy-density ceramic-based capacitors.Although significant successes have been achieved in obtaining high energy densities in lead-based ferroelectric ceramics,the utilization of lead-containing ceramies has been restricted due to environmental and health hazards of lead.Lead-free ferroelectric ceramics have garnered tremendous attention and are expected to replace lead-based ceramics in the near future.However,the energy density of lead-free ceramics is still lagging behind that of lead-containing cou.nterparts,severely limiting their applications.Significant efforts have been made to enhance the energy storage performance of lead-free ceramics using multi-scale design strategies,and exciting progress has been achieved in the past decade.This review briefly discusses the energy storage mechanism and fundamental characteristics of a dielectric capacitor,summarizes and compares the state-of-the-art design strategies for high-energy-density lead-free ceramics,and highlights several critical issues and requirements for industrial production.The prospects and challenges of lead-free ceramics for energy storage applications are also discussed.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
Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelect...Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelectric properties,and electric-field-induced strain was investigated.The X-ray diffraction(XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary(MPB).Doping with an appropriate amount of Eu^(3+) reduces the Fe^(3+) content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d_(33)*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature,which has a Curie temperature(T_C) of 414℃,The unipolar strain and d_(33)* of BF-BT-0.003Eu ceramics increase to 0.438%and 730 pm/V at 125℃ The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT,mainly due to its optimal grain size,reduction of leakage current,and coexistence of ferroelectric-relaxation phases,BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.展开更多
The development of environmentally friendly ceramics for electrostatic energy storage has drawn growing interest due to the wide application in high power and/or pulsed power electronic systems.However,it is difficult...The development of environmentally friendly ceramics for electrostatic energy storage has drawn growing interest due to the wide application in high power and/or pulsed power electronic systems.However,it is difficult to simultaneously achieve ultrahigh recoverable energy storage density(W rec>8 J/cm^(3))and high efficiency(η>80%),which restricts their application in the miniaturized,light weight and easy integrated electronic devices.Herein,the novel NaNbO_(3)-(Bi_(0.8)Sr_(0.2))(Fe_(0.9) Nb_(0.1))O_(3) relaxor antiferro-electric ceramics,which integrates the merits of antiferroelectrics and relaxors,are demonstrated to exhibit stabilized antiferroelectric phase and enhanced dielectric relaxor behavior.Of particular impor-tance is that the 0.88NN-0.12BSFN ceramic achieves giant electric breakdown strength E_(b)=98.3 kV/mm,ultrahigh W _(rec)=16.5 J/cm^(3) and high h=83.3%,as well as excellent frequency,cycling and thermal reliability simultaneously.The comprehensive energy storage performance of NN-BSFN not only out-performs state-of-the-art dielectric ceramics by comparison,but also displays outstanding potential for next-generation energy storage capacitors.展开更多
High-performance lead-free dielectric ceramics with simultaneously high energy storage density and power density are in high demanded for pulse power systems.To realize excellent energy-storage characteristics,a strat...High-performance lead-free dielectric ceramics with simultaneously high energy storage density and power density are in high demanded for pulse power systems.To realize excellent energy-storage characteristics,a strategy to enhance antiferroelectricity and construct a local random field simultaneously was proposed in this study.Based on the above strategy,a series of(1-x)NaNbO_(3)-xBi(Ni_(1/2)Sn_(1/2))O3[xBNS,x=0.05,0.10,0.15,0.20,and 0.22]solid solutions were designed and fabricated.An ultrahigh energy storage density(Utotal)of 7.35 J/cm^(3),and recoverable energy density(Urec)of 5.00 J/cm^(3) were achieved in the 0.10BNS ceramics.In addition,an adequate stability of energy storage properties at a range of temperatures(20e140℃),frequencies(1e100 Hz),and fatigue test durations(1e1-10^(4) cycles)were realized in 0.10BNS ceramics.0.10BNS ceramics displayed a high current density of 1005 A/cm2,an ultrahigh power density of 100.5 MW/cm^(3,)and an ultrashort discharge time of 46.5 ns?This remarkable performance not only justified our strategy but also confirmed 0.10BNS ceramics as a promising candidate for energy storage.展开更多
This paper investigates the pyroelectric of poled antiferroelectric (AFE) ceramic Pbo.97Lao.02 (Zro.69Sno.196 Ti0.114)03 and its remnant polarization dependence of hydrostatic pressure. The results show that the b...This paper investigates the pyroelectric of poled antiferroelectric (AFE) ceramic Pbo.97Lao.02 (Zro.69Sno.196 Ti0.114)03 and its remnant polarization dependence of hydrostatic pressure. The results show that the bound charges of poled sample can be released in short time by temperature field or pressure field. The released charge abruptly forms a large pulse current. The phenomena of released charge under external fields result in the ferroelectric-AFE phase transition induced by temperature or hydrostatic pressure.展开更多
The K_xNa_((1-x))NbO_3(x=0.45, 0.46, 0.47, 0.48, 0.49, 0.50) lead-free piezoelectric ceramics was fabricated by conventional solid-state sintering method. It was found that the ratio of alkaline metal would affect the...The K_xNa_((1-x))NbO_3(x=0.45, 0.46, 0.47, 0.48, 0.49, 0.50) lead-free piezoelectric ceramics was fabricated by conventional solid-state sintering method. It was found that the ratio of alkaline metal would affect the microstructure, bulk density, and optimum sintering temperatures of ceramics. Meanwhile, the electrical properties were also influenced by modulating the K/Na ratio, exhibiting corresponding composition-dependent properties. The optimum electrical properties of K_xNa_((1-x))NbO_3 such as piezoelectric constant d_(33) = 115 pC/N, mechanical quality factor Q_m = 20, Curie temperature Tc = 365 ~oC, ε_(33)~T/ε_0= 588.1, dielectric loss tan δ = 0.024, bulk density(ρ) = 3.08 g/cm^3, remnant polarization(P_r) = 8.87 μC/cm^2 and coercive field(Ec) = 13.79 kV/cm were obtained at x = 0.46.展开更多
基金Funded by the National Natural Science Foundation of China (No.61704113)the Shenzhen Science and Technology Program (No.GJHZ20210705141805015)the Scientific Research Project in School-level (SZIIT2019KJ026)。
文摘To reduce the coercive field of Na_(0.5)Bi_(0.5)TiO_(3),Ba TiO_(3)were added as dopant materials.Then the(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBaTiO_(3)ceramic samples were produced in solid synthetic way.The optimum preparation condition and piezoelectric properties of the samples were investigated.The XRD results show that the fabric transites from rhombohedral to tetragonal gradually with the substitution of the Ba^(2+).The morphotropic phase boundaries(MPB)exists in the composition range of 0.06.
基金Project supported by the National Basic Research Program of China (Grant No.2009CB623306)the International Science & Technology Cooperation Program of China (Grant No.2010DFR50480)the National Natural Science Foundation of China (Grant No.10976022)
文摘Antiferroelectric ferroelectric (AFE-FE) phase transition in ceramic Pbo.97Lao.02(Zro.75Snon36Tion14)O3 (PLZST) was studied by dielectric spectroscopy as functions of frequency (102-105 Hz) and pressure (0-500 MPa) under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were mea- sured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant um dergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE AFE and AFE-FE.
文摘Lead-free piezoelectric ceramics of (Bi1/2Na1/2)TiO3-BaTiO3(BNT-BT) were prepared by the conventional piezoelectric ceramic preparation technique (free air atmosphere sintering). The influence of BaTiO3 additive amount and La2O3 additive amount on the properties of BNT-BT lead-free piezoceramics were investigated. The results show that the dielectric constant(ε) and piezoelectric strain constant(d33) of materials start increasing and then decreasing while BaTiO3 additive amount increasing, the e and d33 of materials have maximum value (ε= 1650, d33 = 120 PC·N -1 ) while x (BaTiO3) =0.06 mol. Theεand d33 of materials start increasing and then decreasing while La2O3 additive amount increasing, the e and d33 of materials have maximum value (ε= 1684, d33 = 153 PC·N-1) while w(La2O3) =0.3% . The influence of La2O3 additive amount on the microstructure of BNT-BT piezoelectric ceramics was analysed by SEM( scanning electron microscope). The influence mechanism of La2O3 additive amount on the properties of BNT-BT piezoelectric ceramics was discussed. The BNT-BT ceramics with optimum comprehensive properties were obtained.
基金supported by the National Natural Science Foundation of China (59972020)
文摘Aim The piezoelectric properties and cytotoxicity of a porous lead-free piezoelectric ceramic for use as a direct bone substitute were investigated. Methodology Cold isostatic pressing (CIP) was applied to fabricate porous lithium sodium potassium niobate (Li0.06Na0.5K0.44) NbO3 specimens using a pore-forming method. The morphologies of the CIP-processed specimens were characterized and compared to those of specimens made by from conventional pressing procedures. The effects of the ceramic on the attachment and proliferation of osteoblasts isolated from the cranium of 1-day-old Sprague- Dawley rats were examined by a scanning electron microscopy (SEM) and metbylthiazol tetrazolium (MTT) assay. Results The results showed that CIP enhanced piezoelectricity and biological performance of the niobate specimen, and also promoted an extracellular matrix-like topography of it. In vitro studies showed that the CIP-enhanced material had positive effects on the attachment and proliferation of osteoblasts. Conclusion Niobate ceramic generated by CIP shows a promise for being a piezoelectric composite bone substitute.
文摘Lead-free piezoelectric (K0.5sNa0.5)1-xLixNbO3 (x = 0at%-20at%) ceramics were synthesized by spark plasma sintering (SPS) at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of (K0.5Na0.5)NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the (K0.5Na0.5)1-xLixNbO3 ceramics.
基金Funded by the Scientific Research Fund of Sichuan Provincial Education Department(No.11ZB109)
文摘CuO-doped(Ag0.75Li0.1Na0.1K0.05)NbO3(ALNKN-xCuO, x = 0.2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2NbrO16- type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with'the grain size of about 1 ~tm was formed for the ceramics with 0.5mo1% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = lm01% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.
基金financially supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20090006110010)Beijing Natural Science Foundation(No.2112028)
基金the National Natural Science Foundation of China (No. 50842028)the National High-Tech Research and Development Program of China (No. 2006AA03Z436).
文摘Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and...
基金supported by the National Natural Science Foundation of China (No. 50842028)the National Basic Research Priorities Program of China (No. 2007CB613301)
文摘Lead-free piezoelectric NaxK1-xNbO3(x = 0.3-0.8)(NKN) ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary(MPB) in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10804130 and 60871027)the Natural Science Foundation of Shaanxi Province of China (Grant No. 2009JQ1001)the Funds of the Key Laboratory of Electrical Insulation and Power Equipment (Grant No. EIPE10202)
文摘Effects of A-site non-stoichiometry on the structural and electrical properties of 0.96K0.5+xNa0.5+xNbO3- 0.04LiSbO3 lead-free piezoelectric ceramics were examined for 0 ≤ x ≤0.02. The piezoelectric coefficients exhibited a maximum, d33 = 187 pC/N at x = 0.0075, coinciding with the maximum of the grain size and the apparent density at x = 0.0075. The apparent density and the piezoelectric coefficients decreased with increasing x at higher x which was likely due to the crystal geometrical distortion of 0.96K0.5+xNa0.5+xNbO3-0.04LiSbO3. In addition, super-large grains were found and this may be due to liquid phase sintering. Excess (K++Na+) attracted a sum of space charges to keep the charge neutral, resulting in charge leakage during the course of ceramic polarization, influencing the piezoelectric and ferroelectric properties. These findings are of importance for guiding the design of Ko.sNao.sNbO3-based lead-free ceramics with enhanced electrical properties.
基金Supported by Program for New Century Excellent Talents in University(No.NCET-07-0329)
文摘The microstructures and electrical properties of Bi0.5(Na1-x-yKxLiy)0.5TiO3 lead-free piezoelectric ceramics were studied.These ceramics were prepared by conventional ceramic technique.XRD analysis reveals that the ceramics possess almost pure perovskite phase when y≤0.2.The SEM results show that,with more amounts of Li+,the crystalline grain growing speed is accelerated,and the sintering temperature can effectively be decreased.The measurements of piezoelectric properties indicate that the ceramics with relatively low amount of Li+ and high amount of K+ have comparatively large piezoelectricity.The dielectric measurements show that the ceramics have properties like relaxor ferroelectrics and diffuse phase transition(DPT) at Td and Tc,respectively.The results of ferroelectric measurements reveal the system has relatively higher remanent polarization Pr(27.6 μC/cm2) and lower coercive field Ec(37.5 kV/cm).
基金supported by the Royal Society Research Grant(RGSR1221252).
文摘It is crucial to discover lead-free materials with ultrahigh recoverable energy density(Wrec)that can be employed in future pulse power capacitors.In this work,a high Wrec of 4.51 J/cm^(3) was successfully obtained in lead-free Nd-doped AgNb_(0.8)Ta_(0.2)O_(3) antiferroelectric ceramics at an applied electric field of 290 kV/cm.It is discovered that Nd doping paired with Nb-site vacancies could stabilize the antiferroelectric phase by lowering the temperatures of the M1-M2 and M2-M3 phase transitions,which leads to higher energy storage efficiency.Furthermore,Nd and Ta co-doping will contribute to the electrical homogeneity and low electrical conductivity,resulting in large breakdown strengths.Aliovalent doping in Ag-site with Nb-site vacancies serves as a novel strategy for the construction of AgNbO_(3)-based ceramics with excellent energy storage performance.
基金supported by the National Natural Science Foundation of China(NSFC)Grants 12174001 and 51872001(C.Wang)NSFC Grant 12104001Anhui Provincial Natural Science Foundation of Grant 2008085QE205(F.Li).
文摘In this work,(1−x)(0.92NaNbO_(3)-0.08BaTiO_(3))-xCa_(0.7)La_(0.2)TiO_(3)(NNBT-xCLT)ceramics were successfully designed and prepared by the solid-state reaction method.Investigations on the structure,dielectric,and energy storage properties were performed.The NNBT-0.25CLT ceramic with orthorhombic phase at room temperature was found to exhibit extremely small grain size and compacted microstructure.A large Wrec of 3.1 J/cm^(3) and a highηof 91.5%under the electric field of 360 kV/cm were achieved simultaneously in the sample.In addition,the energy storage performance of the sample exhibits thermal stability over the temperature range of 25-140°C and the frequency range of 5-500 Hz.The charge and discharge tests reveal that the ceramic shows a large current density CD of 965 A/cm2 and power density PD of 154 MW/cm^(3).This work demonstrates that the NNBT-0.25CLT ceramic is a prospective energy storage material for potential application in the field of pulsed power devices.
基金supported by the National Science Foundation of China(No.61631166004)Shenzhen Science and Technology Program(Grant Nos.KQTD20180411143514543 and JCYJ20180504165831308)Guangdong Provincial Key Laboratory Program(Grant No.2021B1212040001)。
文摘A greater number of compact and reliable electrostatic capacitors are in demand due to the Internet of Things boom and rapidly growing complex and integrated electronic systems,continuously promoting the development of high-energy-density ceramic-based capacitors.Although significant successes have been achieved in obtaining high energy densities in lead-based ferroelectric ceramics,the utilization of lead-containing ceramies has been restricted due to environmental and health hazards of lead.Lead-free ferroelectric ceramics have garnered tremendous attention and are expected to replace lead-based ceramics in the near future.However,the energy density of lead-free ceramics is still lagging behind that of lead-containing cou.nterparts,severely limiting their applications.Significant efforts have been made to enhance the energy storage performance of lead-free ceramics using multi-scale design strategies,and exciting progress has been achieved in the past decade.This review briefly discusses the energy storage mechanism and fundamental characteristics of a dielectric capacitor,summarizes and compares the state-of-the-art design strategies for high-energy-density lead-free ceramics,and highlights several critical issues and requirements for industrial production.The prospects and challenges of lead-free ceramics for energy storage applications are also discussed.
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Project supported by the National Natural Science Foundation of China Youth Project (51702317)the Youth Project of the Natural Science Foundation of Jiangxi Provincial Science and Technology (20212BAB214019)the Program of Qingjiang Excellent Young Talents of Jiangxi University of Science and Technology (JXUSTQJYX2020004)。
文摘Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelectric properties,and electric-field-induced strain was investigated.The X-ray diffraction(XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary(MPB).Doping with an appropriate amount of Eu^(3+) reduces the Fe^(3+) content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d_(33)*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature,which has a Curie temperature(T_C) of 414℃,The unipolar strain and d_(33)* of BF-BT-0.003Eu ceramics increase to 0.438%and 730 pm/V at 125℃ The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT,mainly due to its optimal grain size,reduction of leakage current,and coexistence of ferroelectric-relaxation phases,BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.
基金This work was supported by National Key R&D Program of China(Grant No.2020YFA0711504)the Natural Science Foundation of China(12004181,52073144)+1 种基金Natural Science Foundation of Jiangsu Province(BK20200473,BK20201301)the Fundamental Research Funds for the Central Universities(30919011298).
文摘The development of environmentally friendly ceramics for electrostatic energy storage has drawn growing interest due to the wide application in high power and/or pulsed power electronic systems.However,it is difficult to simultaneously achieve ultrahigh recoverable energy storage density(W rec>8 J/cm^(3))and high efficiency(η>80%),which restricts their application in the miniaturized,light weight and easy integrated electronic devices.Herein,the novel NaNbO_(3)-(Bi_(0.8)Sr_(0.2))(Fe_(0.9) Nb_(0.1))O_(3) relaxor antiferro-electric ceramics,which integrates the merits of antiferroelectrics and relaxors,are demonstrated to exhibit stabilized antiferroelectric phase and enhanced dielectric relaxor behavior.Of particular impor-tance is that the 0.88NN-0.12BSFN ceramic achieves giant electric breakdown strength E_(b)=98.3 kV/mm,ultrahigh W _(rec)=16.5 J/cm^(3) and high h=83.3%,as well as excellent frequency,cycling and thermal reliability simultaneously.The comprehensive energy storage performance of NN-BSFN not only out-performs state-of-the-art dielectric ceramics by comparison,but also displays outstanding potential for next-generation energy storage capacitors.
基金supported by Natural Science Foundation of China(Nos.12064007,11664008 and 61761015)Natural Science Foundation of Guangxi(Nos.2018GXNSFFA050001,2017GXNSFDA198027and 2017GXNSFFA198011)。
文摘High-performance lead-free dielectric ceramics with simultaneously high energy storage density and power density are in high demanded for pulse power systems.To realize excellent energy-storage characteristics,a strategy to enhance antiferroelectricity and construct a local random field simultaneously was proposed in this study.Based on the above strategy,a series of(1-x)NaNbO_(3)-xBi(Ni_(1/2)Sn_(1/2))O3[xBNS,x=0.05,0.10,0.15,0.20,and 0.22]solid solutions were designed and fabricated.An ultrahigh energy storage density(Utotal)of 7.35 J/cm^(3),and recoverable energy density(Urec)of 5.00 J/cm^(3) were achieved in the 0.10BNS ceramics.In addition,an adequate stability of energy storage properties at a range of temperatures(20e140℃),frequencies(1e100 Hz),and fatigue test durations(1e1-10^(4) cycles)were realized in 0.10BNS ceramics.0.10BNS ceramics displayed a high current density of 1005 A/cm2,an ultrahigh power density of 100.5 MW/cm^(3,)and an ultrashort discharge time of 46.5 ns?This remarkable performance not only justified our strategy but also confirmed 0.10BNS ceramics as a promising candidate for energy storage.
基金supported by the National Basic Research Program of China (973 Program) (Grant No. 2009CB623306)the National Natural Science Foundation of China (Grant No. 60528008)+1 种基金the Key Science and Technology Research Project from the Ministry of Education of China (Grant No. 108180)the National Natural Science Foundation of China-NSAF (Grant No. 10976022)
文摘This paper investigates the pyroelectric of poled antiferroelectric (AFE) ceramic Pbo.97Lao.02 (Zro.69Sno.196 Ti0.114)03 and its remnant polarization dependence of hydrostatic pressure. The results show that the bound charges of poled sample can be released in short time by temperature field or pressure field. The released charge abruptly forms a large pulse current. The phenomena of released charge under external fields result in the ferroelectric-AFE phase transition induced by temperature or hydrostatic pressure.
基金Funded by the National Natural Science Foundation of China(No.51302199)Key Natural Science Foundation of Hubei Province of China for Distinguished Yong Scholars(No.2014CFA044)+2 种基金Cultivation Plan for Science and Technology Talents of Wu Han City(No.2014072704011253)MOST Special Fund from the State Key Laboratory of Geological Process and Mineral Resources(No.MSFGPMR201204)Natural Science Foundation of Hubei Province(No.2014CFB809)
文摘The K_xNa_((1-x))NbO_3(x=0.45, 0.46, 0.47, 0.48, 0.49, 0.50) lead-free piezoelectric ceramics was fabricated by conventional solid-state sintering method. It was found that the ratio of alkaline metal would affect the microstructure, bulk density, and optimum sintering temperatures of ceramics. Meanwhile, the electrical properties were also influenced by modulating the K/Na ratio, exhibiting corresponding composition-dependent properties. The optimum electrical properties of K_xNa_((1-x))NbO_3 such as piezoelectric constant d_(33) = 115 pC/N, mechanical quality factor Q_m = 20, Curie temperature Tc = 365 ~oC, ε_(33)~T/ε_0= 588.1, dielectric loss tan δ = 0.024, bulk density(ρ) = 3.08 g/cm^3, remnant polarization(P_r) = 8.87 μC/cm^2 and coercive field(Ec) = 13.79 kV/cm were obtained at x = 0.46.