The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） con...The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.展开更多
CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly inve...CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly investigated in the frequency of 102-106 Hz,which is far low to clarify the intrinsic dielectric feature.So,microwave dielectric properties have been investigated for the CCTO porous ceramics sintered at low temperature(≤1000°C).Good microwave dielectric properties of permittivityε=62.7,quality factor Qf=3062 GHz and temperature coefficient of the resonant frequencyτf=179 ppm/°C are achieved for the CCTO ceramics sintered at 1000°C,the dielectric loss significantly decreases two orders to 0.002 compared to that of CCTO ceramics sintered at critical temperature of 1020°C confirmed by differential scanning calorimetry(DSC).This clue indicates that giant permittivity and high loss is not intrinsic for CCTO ceramics,but derives from composition segregation,liquid phase and defects associated with internal barrier layer capacitor(IBLC).It suggests that CCTO-based ceramics is a promising microwave dielectric materials with high permittivity.展开更多
Lead-free(K_(0.4425)Na_(0.52)Li_(0.0375))(Nb_(0.8825)Sb_(0.07)Ta_(0.0475))O_(3)(KNLNST)piezoelectric ceramics are synthesized by the conventional solid-state reaction method.The sintering temperature and poling temper...Lead-free(K_(0.4425)Na_(0.52)Li_(0.0375))(Nb_(0.8825)Sb_(0.07)Ta_(0.0475))O_(3)(KNLNST)piezoelectric ceramics are synthesized by the conventional solid-state reaction method.The sintering temperature and poling temperature dependence of ceramic properties are investigated.Previous studies have shown that variation of sintering temperature can cause phase transition,similar to the morphotropic phase boundary(MPB)behavior induced by composition changes in Pb(Zr,Ti)O_(3)(PZT).And the best piezoelectric performance can be obtained near the phase-transition sintering temperature.In this research,phase transition induced by sintering temperature cannot be detected and excellent piezoelectric properties can still be obtained.The sintering temperature of the largest piezoelectric coefficient of such composition is lower than that of the highest density,which is considered in composition segregation as a result of intensified volatilization of alkali metal oxides.Combined with the effect of poling temperature,the peak values of the piezoelectric properties are d_(33)=313 pC/N,k_(p)=47%,ε_(r)=1825,tanδd=0.024,T_(o-t)=88℃,and TC=274℃.展开更多
Nickel-zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials.Nickel-zinc ferrite nanoparticles with composition Ni_(0.5)Zn_(0.5)Fe...Nickel-zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials.Nickel-zinc ferrite nanoparticles with composition Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)were prepared using mechanical alloying to analyze the effect of sintering temperature on microstructure evolution of a single sample with dielectric properties.The single sample with nanosized pellet was sintered from 600℃to 1200℃and analyzed by X-ray diffraction(XRD)to investigate the phases of the powders and by field emission scanning electron microscopy(FESEM)for the morphology and microstructure analyses.Dielectric properties such as dielectric constant(e″)and dielectric loss(e′)were studied as functions of frequency and temperature for Ni_(0.5)Zn_(0.5)Fe_(2)O_(4).The dielectric properties of the sample were measured using HP 4192A LF impedance analyzer in the low frequency range from 40 Hz to 1 MHz and at temperature ranging from 30℃to 250℃.The results showed that single phase Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)cannot be formed by milling alone and therefore requires sintering.The crystallization of the ferrite sample increased with increasing sintering temperature,while the porosity decreased and the density and average grain size increased.Evolution of the microstructure resulted in three activation energies of grain growth,where above 850℃there was a rapid grain growth in the microstructure.Dielectric constant and loss factor decreased with the increase in frequency.The optimum sintering temperature of Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)was found to be 900℃which had high dielectric constant and low dielectric loss.展开更多
Low-temperature sintering and properties of LTCC(low temperature co-fired ceramics) materials based on CaO-BaO-Al2O3-B2O3-SiO2 glass and various fillers such as Al2O3, silica glass, christobalite, AlN, ZrO2, MgO·...Low-temperature sintering and properties of LTCC(low temperature co-fired ceramics) materials based on CaO-BaO-Al2O3-B2O3-SiO2 glass and various fillers such as Al2O3, silica glass, christobalite, AlN, ZrO2, MgO·SiO2, TiO2 were investigated. The results show that densification, crystallization, microstructures and dielectric properties of the composites are found to strongly depend on the type of filler. The densification process of glass/ceramic composites with various fillers is mainly from 600 °C to 925 °C, and the initial compacting temperature of samples is 600 °C. The initial rapid densification of samples starts at its glass softening temperature. LTCC compositions containing Al2O3, silica glass, AlN and MgO·SiO2 fillers start to have the crystallization peaks at 890, 903, 869 and 844 °C, respectively. The crystallization peaks are believed as correlated to the crystallization of CaAl2SiO8, β-SiO2, Ca2Al2SiO7 and β-SiO2. The composite ceramic with Al2O3, silica glass and TiO2 ceramic have a better dense structure and better smooth fracture surface. Sample for Al2O3 has the lowest dielectric loss tanδ value of 0.00091, whereas the sample for MgO·SiO2 has the highest dielectric loss tanδ value of 0.02576. The sample for TiO2 has the highest dielectric constant value of 14.46, whereas the sample for AlN has the lowest dielectric constant value of 4.61.展开更多
Magnetic properties of diluted magnetic semiconductors (DMSs), Ni-doped ZnO materials, prepared by sol-gel method were investigated by measuring magnetization as functions of magnetic field. The Ni content affects the...Magnetic properties of diluted magnetic semiconductors (DMSs), Ni-doped ZnO materials, prepared by sol-gel method were investigated by measuring magnetization as functions of magnetic field. The Ni content affects the magnetic properties at low sintered temperature but it has few effects on the magnetic properties at high sintered temperature. The sintered temperature has great effects on the magnetic properties of Ni/ZnO at high original mole ratio of Ni/Zn while it has slight effects on the magnetic properties of Ni/ZnO at low original mole ratio of Ni/Zn whatever low or high sintered temperature.展开更多
The influence of MgO on sintering and dielectric properties of La2O3-TiO2 ceramics was investigated, and the mechanism also discussed. The results show that La2O3-TiO2 ceramics with MgO can be sintered between 1200 an...The influence of MgO on sintering and dielectric properties of La2O3-TiO2 ceramics was investigated, and the mechanism also discussed. The results show that La2O3-TiO2 ceramics with MgO can be sintered between 1200 and 1280 ℃. With the increasing of the MgO, the dielectric constant of the material decreases, but the temperature coefficient of dielectric constant increases. Between 1 and 40 MHz,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 densified the microstructure with a decreased grain size. The highest relative density reached more than 90%. The highest piezoelectric dielectric coefficient d33 and planar mode electro-mechanical coupling coefficient kp were 110 pC/N and 19.5%,which were obtained in the NKNT ceramic with 1 mol% Ti. The piezoelectric properties of the NKNT ceramics were enhanced by aging in air for a period of time owing to the compensation of oxygen vacancies.展开更多
文摘The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.
基金supported by the National Natural Science Foundation of China(No.51602055).
文摘CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly investigated in the frequency of 102-106 Hz,which is far low to clarify the intrinsic dielectric feature.So,microwave dielectric properties have been investigated for the CCTO porous ceramics sintered at low temperature(≤1000°C).Good microwave dielectric properties of permittivityε=62.7,quality factor Qf=3062 GHz and temperature coefficient of the resonant frequencyτf=179 ppm/°C are achieved for the CCTO ceramics sintered at 1000°C,the dielectric loss significantly decreases two orders to 0.002 compared to that of CCTO ceramics sintered at critical temperature of 1020°C confirmed by differential scanning calorimetry(DSC).This clue indicates that giant permittivity and high loss is not intrinsic for CCTO ceramics,but derives from composition segregation,liquid phase and defects associated with internal barrier layer capacitor(IBLC).It suggests that CCTO-based ceramics is a promising microwave dielectric materials with high permittivity.
基金This study was supported by the National Natural Science Foundation of China(No.51172108)the project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Lead-free(K_(0.4425)Na_(0.52)Li_(0.0375))(Nb_(0.8825)Sb_(0.07)Ta_(0.0475))O_(3)(KNLNST)piezoelectric ceramics are synthesized by the conventional solid-state reaction method.The sintering temperature and poling temperature dependence of ceramic properties are investigated.Previous studies have shown that variation of sintering temperature can cause phase transition,similar to the morphotropic phase boundary(MPB)behavior induced by composition changes in Pb(Zr,Ti)O_(3)(PZT).And the best piezoelectric performance can be obtained near the phase-transition sintering temperature.In this research,phase transition induced by sintering temperature cannot be detected and excellent piezoelectric properties can still be obtained.The sintering temperature of the largest piezoelectric coefficient of such composition is lower than that of the highest density,which is considered in composition segregation as a result of intensified volatilization of alkali metal oxides.Combined with the effect of poling temperature,the peak values of the piezoelectric properties are d_(33)=313 pC/N,k_(p)=47%,ε_(r)=1825,tanδd=0.024,T_(o-t)=88℃,and TC=274℃.
基金The authors acknowledge the Fundamental Research Grant Scheme(FRGS)Project No.01-04-10-862 FR,Graduate Research Fellowship given to the graduate student(Rafidah Hassan)and the Physics Department,Faculty of Science,UPM.
文摘Nickel-zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials.Nickel-zinc ferrite nanoparticles with composition Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)were prepared using mechanical alloying to analyze the effect of sintering temperature on microstructure evolution of a single sample with dielectric properties.The single sample with nanosized pellet was sintered from 600℃to 1200℃and analyzed by X-ray diffraction(XRD)to investigate the phases of the powders and by field emission scanning electron microscopy(FESEM)for the morphology and microstructure analyses.Dielectric properties such as dielectric constant(e″)and dielectric loss(e′)were studied as functions of frequency and temperature for Ni_(0.5)Zn_(0.5)Fe_(2)O_(4).The dielectric properties of the sample were measured using HP 4192A LF impedance analyzer in the low frequency range from 40 Hz to 1 MHz and at temperature ranging from 30℃to 250℃.The results showed that single phase Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)cannot be formed by milling alone and therefore requires sintering.The crystallization of the ferrite sample increased with increasing sintering temperature,while the porosity decreased and the density and average grain size increased.Evolution of the microstructure resulted in three activation energies of grain growth,where above 850℃there was a rapid grain growth in the microstructure.Dielectric constant and loss factor decreased with the increase in frequency.The optimum sintering temperature of Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)was found to be 900℃which had high dielectric constant and low dielectric loss.
基金Project supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions ChinaProject(CXZZ12_0415) supported by Innovation Foundation for Graduate Students of Jiangsu Province ChinaProject(IRT1146) supported by Changjiang Scholars and Innovative Research Team in University(PCSIRT),China
文摘Low-temperature sintering and properties of LTCC(low temperature co-fired ceramics) materials based on CaO-BaO-Al2O3-B2O3-SiO2 glass and various fillers such as Al2O3, silica glass, christobalite, AlN, ZrO2, MgO·SiO2, TiO2 were investigated. The results show that densification, crystallization, microstructures and dielectric properties of the composites are found to strongly depend on the type of filler. The densification process of glass/ceramic composites with various fillers is mainly from 600 °C to 925 °C, and the initial compacting temperature of samples is 600 °C. The initial rapid densification of samples starts at its glass softening temperature. LTCC compositions containing Al2O3, silica glass, AlN and MgO·SiO2 fillers start to have the crystallization peaks at 890, 903, 869 and 844 °C, respectively. The crystallization peaks are believed as correlated to the crystallization of CaAl2SiO8, β-SiO2, Ca2Al2SiO7 and β-SiO2. The composite ceramic with Al2O3, silica glass and TiO2 ceramic have a better dense structure and better smooth fracture surface. Sample for Al2O3 has the lowest dielectric loss tanδ value of 0.00091, whereas the sample for MgO·SiO2 has the highest dielectric loss tanδ value of 0.02576. The sample for TiO2 has the highest dielectric constant value of 14.46, whereas the sample for AlN has the lowest dielectric constant value of 4.61.
基金This work was financially supported by Korea Research Foundation of the Korea Government(MOEHRD)(KRF-2005-210-C00024).
文摘Magnetic properties of diluted magnetic semiconductors (DMSs), Ni-doped ZnO materials, prepared by sol-gel method were investigated by measuring magnetization as functions of magnetic field. The Ni content affects the magnetic properties at low sintered temperature but it has few effects on the magnetic properties at high sintered temperature. The sintered temperature has great effects on the magnetic properties of Ni/ZnO at high original mole ratio of Ni/Zn while it has slight effects on the magnetic properties of Ni/ZnO at low original mole ratio of Ni/Zn whatever low or high sintered temperature.
文摘The influence of MgO on sintering and dielectric properties of La2O3-TiO2 ceramics was investigated, and the mechanism also discussed. The results show that La2O3-TiO2 ceramics with MgO can be sintered between 1200 and 1280 ℃. With the increasing of the MgO, the dielectric constant of the material decreases, but the temperature coefficient of dielectric constant increases. Between 1 and 40 MHz,
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 densified the microstructure with a decreased grain size. The highest relative density reached more than 90%. The highest piezoelectric dielectric coefficient d33 and planar mode electro-mechanical coupling coefficient kp were 110 pC/N and 19.5%,which were obtained in the NKNT ceramic with 1 mol% Ti. The piezoelectric properties of the NKNT ceramics were enhanced by aging in air for a period of time owing to the compensation of oxygen vacancies.
