High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based...High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated.The Bi2O3 ,acting as a sintering additive,can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130 °C.The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasingBi2O3 content.The dielectric constant increased with increasingBi2O3 until it reached the maximum value with 0.8 mol%Bi2O3 additive,and the dielectric loss decreased with increasingBi2O3 content.Optimal dielectric properties of ε=2470,tanδ=0.011 and △ε/ε 25 ≤±9%（-55-150 °C） were obtained for the BaTiO3-based ceramics doped with 0.8 mol%Bi2O3 sintered at 1130 °C for 6 h.展开更多
Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,a...Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,and 8 wt.%)on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment.The results show that increasing the Al_(2)O_(3) doping contents(0−8 wt.%)reduces the porosity(21.74%−10.08%)and roughness(3.22−1.34μm)of the shell surface.The increase in Cr_(2)O_(3) dopant content(2−8 wt.%)further exacerbates the interfacial reaction,leading to an increase in the thickness of the reaction layer(2.6−3.1μm)and a decrease in the wetting angle(93.9°−91.0°).The addition of Al_(2)O_(3) and TiO_(2) dopants leads to the formation of Al_(2)TiO_(5) composite oxides in the reaction products,which effectively inhibits the interfacial reaction.The increase in TiO_(2) dopant contents(0−8 wt.%)further promotes the formation of Al_(2)TiO_(5),which decreases the thickness of the interfacial reaction layer(3.9−1.2μm)and increases the wetting angle(95.0°−103.8°).The introduced dopants enhance the packing density of the shell surface,while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.展开更多
Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several chall...Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.展开更多
Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average gra...Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average grain size and guaranteed the reliability,while the bigger-grained powder enhanced the dielectric constant.Various percentages of bigger-grained BT powder were introduced to balance the average grain size and the dielectric constant.As the proportion of bigger grains increased,the dielectric constant(εr)improved significantly.The room-temperatureεr of 25%bigger-grain mixed BT(2623)was~50%higher than that of the sample with a similar average grain size without grain grading.The ceramic mixed with 15%bigger-grained BT showed comprehensive dielectric performance,which met the EIA X5R standard and provided a considerableεr of 1841 along with a low dielectric loss of 0.78%.Notably,the average grain size was 90 nm,which favors the applications in ultra-thin multilayer ceramic capacitors.展开更多
In recent decades,many additives with difierent characteristics have been applied to strengthen and toughen Al_2O_(3)一based ceramic cutting tool materials.Among them,SiC whiskers and SiC nanoparticles showed excellen...In recent decades,many additives with difierent characteristics have been applied to strengthen and toughen Al_2O_(3)一based ceramic cutting tool materials.Among them,SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties.W hile no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening efects of them have not been studied.An Al_2O_(3)一SiCw-SiCno advanced ceramic cutting tool material is fabricated by adding both one--dimensional SiC whiskers and zero--dimensional SiC nanoparticles into the Al_2O_(3)matrix with an efective dispersing and mixing process.The composites with 25 vo1%SiC whiskers and 25 vo1%SiC nanoparticles alone are also investegated for comparison purposes.Results show that the Al_2O_(3)一SiCw-SiCno composite with both 20 vo1%SiC whiskers and 5 vo1%SiC nanoparticles additives have much improved mechanical properties.The flexural strength of Al_2O_(3)-SiCw-SiCⅡD is 730~95 MPa and fracture toughness is 5.6±0.6 MPa’m.The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination.It is indicated that when SiC whiskers and nanoparticles are added together,the grains are further refined and homogenized,so that the microstructure and fracture mode ratio is modified.The SiC nanoparticles are found helpful to enhance the toughening efects of the SiC whiskers.The proposed research helps to enrich the types of ceramic cutting too1 and is benefit to expand the application range of ceramic cutting too1.展开更多
Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic fi...Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic filters by using microporous corundum-spinel raw materials to replace dense raw materials.Three kinds of Al_(2)O_(3)-based ceramic filters fabricated from dense α-Al_(2)O_(3) micro-powder or microporous corundum-spinel powder were selected to carry out the immersion tests with molten steel.On the one hand,the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten steel.On the other hand,the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of skeleton.The reaction process at the solid-liquid interface also improved the wettability of the interface between skeleton and molten steel,resulting in a larger penetration depth and a better adsorption effect on the inclusions.In summary,the novel Al_(2)O_(3)-based ceramic filter prepared with microporous corundum-spinel powder and addition of 5 wt.% nano-Al_(2)O_(3) powder reduced the total oxygen content of the steel from 40.2×10^(-4) to 12.7×10^(-4) wt.% by 68.4% and the Al content from 0.46 to 0.18 wt.% by 60.9% after immersion test,presenting the most excellent purification performance on molten steel.展开更多
Outstanding electric performance can be achieved in the textured ceramics.Therefore,the Ba_(0.85)Ca_(0.15)Zr_(0.09)Ti_(0.91)O_(3)(BCZT)lead-free piezoceramics with high texture degree(f)in<001>direction were suc...Outstanding electric performance can be achieved in the textured ceramics.Therefore,the Ba_(0.85)Ca_(0.15)Zr_(0.09)Ti_(0.91)O_(3)(BCZT)lead-free piezoceramics with high texture degree(f)in<001>direction were successfully prepared using template grain growth method.On account of the perfect sheet BaTiO3(BT)templates,a texture degree as high as 97.9%for BCZT-3.0 wt%BT ceramics was obtained.The ceramics system exhibited excellent comprehensive electrical properties(d_(33)~575 pCN^(-1),k_(p)~0.61,T_(C)~89℃ε_(r)(20℃)~3002,tanδ~4.18%,P_(r)~10.91μC cm^(-2),E_(C)~2.20 kV cm^(-1)).The superior performance originated from the coexistence of rhombohedralorthorhombic-tetragonal phases(R-O-T),as well as high textured degree.The multiphase coexistence was attributed to the composition design.This work provides a theoretical basis for designing lead-free piezoceramics with excellent properties in the future.展开更多
Copper calcium titanate(CaCu_(3)Ti_(4)O_(12),CCTO)ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integra...Copper calcium titanate(CaCu_(3)Ti_(4)O_(12),CCTO)ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integration.However,the extent of grain and grain boundary contribution to the colossal permittivity of CCTO-based ceramics based on the internal barrier layer capacitor(IBLC)model is still in debate.This affects their electrical performance optimization and real-world applications.In this study,a series of novel lead-free colossal permittivity ceramic s,xLiCuNb_(3)O_(9-)(1-x)CaCu_(3)Ti_(4)O_(12)(LCNOCCTO),were designed and prepared using a solid-phase reaction approach.The colossal permittivity response mechanism of LCNO-CCTO ceramics was further explored by performing the complex impedance spectrum and analyzing the activation energy from the grain and grain boundary contribution viewpoint.As a result,the LCNO-CCTO ceramics present the cubic perovskite structure with the space groups of■.All the LCNOCCTO ceramics exhibit the significantly enhanced colossal permittivity(10^(5))response,and the ceramic with x=0.15 shows the highest permittivity of about 4.64×10^(5)(20 Hz,room temperature)accompanied by a lower grain resistance of 9.61Ωand larger grain activation energy of 0.21 eV.The enhanced colossal permittivity response is primarily attributed to the great electrical response inside grains of LCNO-CCTO ceramics,resulting from a smaller grain resistance.Also importantly,the high-frequency dielectric relaxation characteristics are improved by incorporating the LCNO into CCTO ceramics as an ion form.Accordingly,the LCNO-CCTO ceramics show a suppressed high-frequency dielectric loss.These results can provide a thorough knowledge and useful optimization strategy for developing high-performance colossal permittivity materials.展开更多
Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities thr...Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities through X-ray photoelectron spectrum （XPS）. The results showed that the dielectric characteristics of Nd2O3 doped BaTiO3 ceramics were improved by doping. When Nd2O3 content was 0.003 mol, the results were even better, the dielectric constant was increased, the dielectric loss was decreased, the Curie-temperature （Tc） was 110 ℃, and the frequency characteristic was also good. The resistivity of Nd2O3 doped BaTiO3 ceramics was lower than that of pure BaTiO3 ceramics, when Nd2O3 content was 0.001 mol,the resistivity was （2.364×）108 Ω·m, the smallest. The grain resistance of Nd2O3 doped BaTiO3 ceramics exhibited NTC effect, but the grain boundary resistance showed PTC effect, and the grain boundary resistance was larger than that of the grain resistance, so the PTC effect originated from the grain boundary. The analysis of the element binding energy through X-ray photoelectron spectrum were indicated that the quantivalence of Ba2+and Ti4+in Nd2O3 doped BaTiO3 ceramics was variable, and resulted in the improvement of the conductibility of BaTiO3 ceramics.展开更多
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
Multilayer ceramic capacitors(MLCCs)play a crucial role in pulsed power applications because of their rapid charge/discharge capabilities.However,the combination of high energy density and high efficiency is the main ...Multilayer ceramic capacitors(MLCCs)play a crucial role in pulsed power applications because of their rapid charge/discharge capabilities.However,the combination of high energy density and high efficiency is the main challenge in practical applications.This study presents barium titanate-based(BaTiO_(3)-)lead-free relaxor ferroelectric(RFE)MLCCs formulated with 0.84BaTiO_(3)–0.16Bi(Mg_(0.2)Ni_(0.2)Zn_(0.2)Zr_(0.2)Nb_(0.2))O_(3)(0.84BT–0.16BMNZZN)and platinum inner electrodes via a tape-casting method.The introduction of the high-entropy component BMNZZN effectively enhances the relaxation behavior and local nanodomains while promoting grain refinement,resulting in a comprehensive improvement in insulation performance and energy storage performance.As a result,MLCCs exhibit excellent recoverable energy density(W_(rec)=15.7 J∙cm^(−3))and ultrahigh efficiency(η)of 96.4%(@1614 kV∙cm−1),simultaneously showing good temperature stability over a range of−120‒100℃(W_(rec)≈8.9 J∙cm^(−3)with a variation of less than±4.85%,@1078 kV∙cm−1)and excellent fatigue resistance(W_(rec)≈9.2 J∙cm^(−3)with a variation of less than±0.82%over 107 cycles,andηgreater than 95%,@1078 kV∙cm−1).These findings indicate that BT–BMNZZN RFE MLCCs offer a viable solution for high-power energy storage capacitors.展开更多
Lead-free antiferroelectric(AFE)ceramics are promising candidates for next-generation pulsed power capacitors.However,their practical deployment remains limited by low recoverable energy density(Wrec),limited dielectr...Lead-free antiferroelectric(AFE)ceramics are promising candidates for next-generation pulsed power capacitors.However,their practical deployment remains limited by low recoverable energy density(Wrec),limited dielectric breakdown strength(Eb),and poor efficiency(η),particularly under moderate electric fields.To address these challenges,this study introduces a compositional design strategy that simultaneously engineers both A-and B-sites in AgNbO_(3)(AN)perovskite ceramics.Specifically,20 mol%Ta^(5+)is fixed at the B-site,while dual A-site substitution with Li^(+)and Nd^(3+)is implemented.This codoping approach enables a tunable transition from conventional AFE behavior to a relaxor-antiferroelectric-like(R-AFE-like)state.This evolution is driven primarily by A-site chemical disorder introduced by Li^(+)/Nd^(3+)codoping,which disrupts long-range antiferroelectric ordering and facilitates the formation of nanodomains.In parallel,B-site Ta^(5+)substitution contributes by suppressing octahedral tilting and stabilizing the nonpolar phase.The optimized composition,(Ag_(1−4x)Li_(x)Nd_(x))(Nb_(0.8)Ta_(0.2))O_(3) at x=0.03,delivers a remarkable recoverable energy density of 7.2 J/cm^(3) and an efficiency of 92.3%under a moderate electric field of 327 kV/cm.In addition,this composition demonstrates an excellent Wrec/Eb ratio and capacitor-grade reliability,including strong frequency and thermal stability,as well as ultrafast discharge characteristics(t0.9≈40 ns)with a peak power density of 172 MW/cm^(3).Overall,this work provides a detailed structure-property-performance framework for designing high-efficiency,high-power,lead-free capacitors by harnessing tunable relaxor-antiferroelectricity.展开更多
基金supported by the Tianjin Natural Science Foundation, China (Grant No. 06YFJMJC01000)
文摘High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated.The Bi2O3 ,acting as a sintering additive,can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130 °C.The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasingBi2O3 content.The dielectric constant increased with increasingBi2O3 until it reached the maximum value with 0.8 mol%Bi2O3 additive,and the dielectric loss decreased with increasingBi2O3 content.Optimal dielectric properties of ε=2470,tanδ=0.011 and △ε/ε 25 ≤±9%（-55-150 °C） were obtained for the BaTiO3-based ceramics doped with 0.8 mol%Bi2O3 sintered at 1130 °C for 6 h.
基金supported by the National Natural Science Foundation of China (No. 52374292)China Baowu Low Carbon Metallurgy Innovation Foundation, China (No. BWLCF202309)the Natural Science Foundation of Changsha City, China (No. KQ2208271)。
文摘Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,and 8 wt.%)on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment.The results show that increasing the Al_(2)O_(3) doping contents(0−8 wt.%)reduces the porosity(21.74%−10.08%)and roughness(3.22−1.34μm)of the shell surface.The increase in Cr_(2)O_(3) dopant content(2−8 wt.%)further exacerbates the interfacial reaction,leading to an increase in the thickness of the reaction layer(2.6−3.1μm)and a decrease in the wetting angle(93.9°−91.0°).The addition of Al_(2)O_(3) and TiO_(2) dopants leads to the formation of Al_(2)TiO_(5) composite oxides in the reaction products,which effectively inhibits the interfacial reaction.The increase in TiO_(2) dopant contents(0−8 wt.%)further promotes the formation of Al_(2)TiO_(5),which decreases the thickness of the interfacial reaction layer(3.9−1.2μm)and increases the wetting angle(95.0°−103.8°).The introduced dopants enhance the packing density of the shell surface,while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.
基金financially supported by the National Natural Science Foundation of China(No.52171046)National Natural Science Foundation of China-key programme(No.52234010)the Fundamental Research Funds for the Central Universities and Shaanxi Provincial Key Science and Technology Innovation Team(No.2023-CX-TD-14).
文摘Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.
基金supported by Ministry of Science and Technology of China through The Key Area Research Plan of Guangdong(Grant No.2019B010937001)High-end MLCC Key Project supported by Guangdong Fenghua Advanced Technology Holding Co.,Ltd.(No.20212001429)+1 种基金the National Key Research and Development Program of China(No.2017YFB0406302)the National Natural Science Foundation of China(No.52032005).
文摘Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average grain size and guaranteed the reliability,while the bigger-grained powder enhanced the dielectric constant.Various percentages of bigger-grained BT powder were introduced to balance the average grain size and the dielectric constant.As the proportion of bigger grains increased,the dielectric constant(εr)improved significantly.The room-temperatureεr of 25%bigger-grain mixed BT(2623)was~50%higher than that of the sample with a similar average grain size without grain grading.The ceramic mixed with 15%bigger-grained BT showed comprehensive dielectric performance,which met the EIA X5R standard and provided a considerableεr of 1841 along with a low dielectric loss of 0.78%.Notably,the average grain size was 90 nm,which favors the applications in ultra-thin multilayer ceramic capacitors.
基金Supported by National Natural Science Foundation of China(Grant No.51175305)
文摘In recent decades,many additives with difierent characteristics have been applied to strengthen and toughen Al_2O_(3)一based ceramic cutting tool materials.Among them,SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties.W hile no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening efects of them have not been studied.An Al_2O_(3)一SiCw-SiCno advanced ceramic cutting tool material is fabricated by adding both one--dimensional SiC whiskers and zero--dimensional SiC nanoparticles into the Al_2O_(3)matrix with an efective dispersing and mixing process.The composites with 25 vo1%SiC whiskers and 25 vo1%SiC nanoparticles alone are also investegated for comparison purposes.Results show that the Al_2O_(3)一SiCw-SiCno composite with both 20 vo1%SiC whiskers and 5 vo1%SiC nanoparticles additives have much improved mechanical properties.The flexural strength of Al_2O_(3)-SiCw-SiCⅡD is 730~95 MPa and fracture toughness is 5.6±0.6 MPa’m.The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination.It is indicated that when SiC whiskers and nanoparticles are added together,the grains are further refined and homogenized,so that the microstructure and fracture mode ratio is modified.The SiC nanoparticles are found helpful to enhance the toughening efects of the SiC whiskers.The proposed research helps to enrich the types of ceramic cutting too1 and is benefit to expand the application range of ceramic cutting too1.
基金financially supported by the National Natural Science Foundation of China(Grant No.51974214).
文摘Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic filters by using microporous corundum-spinel raw materials to replace dense raw materials.Three kinds of Al_(2)O_(3)-based ceramic filters fabricated from dense α-Al_(2)O_(3) micro-powder or microporous corundum-spinel powder were selected to carry out the immersion tests with molten steel.On the one hand,the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten steel.On the other hand,the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of skeleton.The reaction process at the solid-liquid interface also improved the wettability of the interface between skeleton and molten steel,resulting in a larger penetration depth and a better adsorption effect on the inclusions.In summary,the novel Al_(2)O_(3)-based ceramic filter prepared with microporous corundum-spinel powder and addition of 5 wt.% nano-Al_(2)O_(3) powder reduced the total oxygen content of the steel from 40.2×10^(-4) to 12.7×10^(-4) wt.% by 68.4% and the Al content from 0.46 to 0.18 wt.% by 60.9% after immersion test,presenting the most excellent purification performance on molten steel.
基金financially supported by the National Natural Science Foundation of China(NSFC Nos.51862003,52472122)Guizhou Provincial Basic Research Program(Natural Science)(No.QKHJC-ZK-2023-266)+1 种基金Natural Science Project of Education Department of Guizhou Province(No.[2022]045)Guizhou University Natural Science Special(special post)Research Fund(No.(2023)17)
文摘Outstanding electric performance can be achieved in the textured ceramics.Therefore,the Ba_(0.85)Ca_(0.15)Zr_(0.09)Ti_(0.91)O_(3)(BCZT)lead-free piezoceramics with high texture degree(f)in<001>direction were successfully prepared using template grain growth method.On account of the perfect sheet BaTiO3(BT)templates,a texture degree as high as 97.9%for BCZT-3.0 wt%BT ceramics was obtained.The ceramics system exhibited excellent comprehensive electrical properties(d_(33)~575 pCN^(-1),k_(p)~0.61,T_(C)~89℃ε_(r)(20℃)~3002,tanδ~4.18%,P_(r)~10.91μC cm^(-2),E_(C)~2.20 kV cm^(-1)).The superior performance originated from the coexistence of rhombohedralorthorhombic-tetragonal phases(R-O-T),as well as high textured degree.The multiphase coexistence was attributed to the composition design.This work provides a theoretical basis for designing lead-free piezoceramics with excellent properties in the future.
基金financially supported by the National Natural Science Foundation of China(No.52202136)the Natural Science Foundation of Jiangxi Province(No.20232BAB204017)+2 种基金the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE24203)Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices(No.EFMD2024002Z)the Innovation Special Foundation Project for Graduate Students of Nanchang Hangkong University(No.YC2024019)
文摘Copper calcium titanate(CaCu_(3)Ti_(4)O_(12),CCTO)ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integration.However,the extent of grain and grain boundary contribution to the colossal permittivity of CCTO-based ceramics based on the internal barrier layer capacitor(IBLC)model is still in debate.This affects their electrical performance optimization and real-world applications.In this study,a series of novel lead-free colossal permittivity ceramic s,xLiCuNb_(3)O_(9-)(1-x)CaCu_(3)Ti_(4)O_(12)(LCNOCCTO),were designed and prepared using a solid-phase reaction approach.The colossal permittivity response mechanism of LCNO-CCTO ceramics was further explored by performing the complex impedance spectrum and analyzing the activation energy from the grain and grain boundary contribution viewpoint.As a result,the LCNO-CCTO ceramics present the cubic perovskite structure with the space groups of■.All the LCNOCCTO ceramics exhibit the significantly enhanced colossal permittivity(10^(5))response,and the ceramic with x=0.15 shows the highest permittivity of about 4.64×10^(5)(20 Hz,room temperature)accompanied by a lower grain resistance of 9.61Ωand larger grain activation energy of 0.21 eV.The enhanced colossal permittivity response is primarily attributed to the great electrical response inside grains of LCNO-CCTO ceramics,resulting from a smaller grain resistance.Also importantly,the high-frequency dielectric relaxation characteristics are improved by incorporating the LCNO into CCTO ceramics as an ion form.Accordingly,the LCNO-CCTO ceramics show a suppressed high-frequency dielectric loss.These results can provide a thorough knowledge and useful optimization strategy for developing high-performance colossal permittivity materials.
文摘Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities through X-ray photoelectron spectrum （XPS）. The results showed that the dielectric characteristics of Nd2O3 doped BaTiO3 ceramics were improved by doping. When Nd2O3 content was 0.003 mol, the results were even better, the dielectric constant was increased, the dielectric loss was decreased, the Curie-temperature （Tc） was 110 ℃, and the frequency characteristic was also good. The resistivity of Nd2O3 doped BaTiO3 ceramics was lower than that of pure BaTiO3 ceramics, when Nd2O3 content was 0.001 mol,the resistivity was （2.364×）108 Ω·m, the smallest. The grain resistance of Nd2O3 doped BaTiO3 ceramics exhibited NTC effect, but the grain boundary resistance showed PTC effect, and the grain boundary resistance was larger than that of the grain resistance, so the PTC effect originated from the grain boundary. The analysis of the element binding energy through X-ray photoelectron spectrum were indicated that the quantivalence of Ba2+and Ti4+in Nd2O3 doped BaTiO3 ceramics was variable, and resulted in the improvement of the conductibility of BaTiO3 ceramics.
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funding from the Natural Science Foundation of Shanghai(Grant No.21ZR1473100)the National Natural Science Foundation of China(Grant Nos.U2002217,51831010,and 5227130).
文摘Multilayer ceramic capacitors(MLCCs)play a crucial role in pulsed power applications because of their rapid charge/discharge capabilities.However,the combination of high energy density and high efficiency is the main challenge in practical applications.This study presents barium titanate-based(BaTiO_(3)-)lead-free relaxor ferroelectric(RFE)MLCCs formulated with 0.84BaTiO_(3)–0.16Bi(Mg_(0.2)Ni_(0.2)Zn_(0.2)Zr_(0.2)Nb_(0.2))O_(3)(0.84BT–0.16BMNZZN)and platinum inner electrodes via a tape-casting method.The introduction of the high-entropy component BMNZZN effectively enhances the relaxation behavior and local nanodomains while promoting grain refinement,resulting in a comprehensive improvement in insulation performance and energy storage performance.As a result,MLCCs exhibit excellent recoverable energy density(W_(rec)=15.7 J∙cm^(−3))and ultrahigh efficiency(η)of 96.4%(@1614 kV∙cm−1),simultaneously showing good temperature stability over a range of−120‒100℃(W_(rec)≈8.9 J∙cm^(−3)with a variation of less than±4.85%,@1078 kV∙cm−1)and excellent fatigue resistance(W_(rec)≈9.2 J∙cm^(−3)with a variation of less than±0.82%over 107 cycles,andηgreater than 95%,@1078 kV∙cm−1).These findings indicate that BT–BMNZZN RFE MLCCs offer a viable solution for high-power energy storage capacitors.
基金supported by the National Research Foundation of Korea(NRF)(Nos.RS-2021-NR060108 and RS-2023-00241159)supported by NRF grants(Nos.RS-2023-NR077116 and RS-2024-00448865).
文摘Lead-free antiferroelectric(AFE)ceramics are promising candidates for next-generation pulsed power capacitors.However,their practical deployment remains limited by low recoverable energy density(Wrec),limited dielectric breakdown strength(Eb),and poor efficiency(η),particularly under moderate electric fields.To address these challenges,this study introduces a compositional design strategy that simultaneously engineers both A-and B-sites in AgNbO_(3)(AN)perovskite ceramics.Specifically,20 mol%Ta^(5+)is fixed at the B-site,while dual A-site substitution with Li^(+)and Nd^(3+)is implemented.This codoping approach enables a tunable transition from conventional AFE behavior to a relaxor-antiferroelectric-like(R-AFE-like)state.This evolution is driven primarily by A-site chemical disorder introduced by Li^(+)/Nd^(3+)codoping,which disrupts long-range antiferroelectric ordering and facilitates the formation of nanodomains.In parallel,B-site Ta^(5+)substitution contributes by suppressing octahedral tilting and stabilizing the nonpolar phase.The optimized composition,(Ag_(1−4x)Li_(x)Nd_(x))(Nb_(0.8)Ta_(0.2))O_(3) at x=0.03,delivers a remarkable recoverable energy density of 7.2 J/cm^(3) and an efficiency of 92.3%under a moderate electric field of 327 kV/cm.In addition,this composition demonstrates an excellent Wrec/Eb ratio and capacitor-grade reliability,including strong frequency and thermal stability,as well as ultrafast discharge characteristics(t0.9≈40 ns)with a peak power density of 172 MW/cm^(3).Overall,this work provides a detailed structure-property-performance framework for designing high-efficiency,high-power,lead-free capacitors by harnessing tunable relaxor-antiferroelectricity.
