共查询到20条相似文献,搜索用时 62 毫秒
1.
Feng Gao Liangliang Liu Bei Xu GuoXin Hu Xiao Cao Rongzi Hong Changsheng Tian 《Journal of the European Ceramic Society》2011,31(15):2987-2996
Plate-like NaNbO3 particles were used as templates to fabricate grain-oriented 0.96(0.8Na0.5Bi0.5TiO3–0.2 K0.5Bi0.5TiO3)–0.04NaNbO3 (NKBT) ceramics. The effects of the sintering temperature and the soaking time on the grain orientation and the microstructure of the textured NKBT ceramics were investigated, and the dielectric relaxor behavior is discussed. The results show that textured ceramics were successfully obtained with orientation factor more than 0.8. The textured ceramics have a microstructure with strip-like grains aligning in the direction parallel to the casting plane. The degree of grain orientation increases initially, then decreases with increasing sintering temperature, and increases continuously with increasing soaking time. The textured NKBT ceramics shows obvious dielectric relaxor characteristics which can be well explained by microdomain–macrodomain transition theory with calculating criterion K. The results show that formation of texture is beneficial to microdomain–macrodomain transition, which lead to weaken relaxor behavior and raise the dielectric constant at Ttr. 相似文献
2.
Microstructure and piezoelectric properties of textured (Na0.84K0.16)0.5Bi0.5TiO3 lead-free ceramics
《Journal of the European Ceramic Society》2007,27(12):3453-3458
Textured (Na,K)0.5Bi0.5TiO3 ceramics were fabricated by reactive-templated grain growth in combination with tape casting. The effects of sintering conditions on the grain orientation and the piezoelectric properties of the textured (Na,K)0.5Bi0.5TiO3 ceramics were investigated. The results show that the textured ceramics have microstructure with plated-like grains aligning in the direction parallel to the casting plane. The ceramics exhibit {h 0 0} preferred orientation and the degree of orientation is larger than 0.7. The degree of grain orientation increases with the increasing sintering temperature. The textured ceramics show anisotropy dielectric and piezoelectric properties in the directions of parallel and perpendicular to the casting plane. The ceramics in the perpendicular direction exhibit better dielectric and piezoelectric properties than those of the nontextured ceramics with the same composition. The optimized sintering temperature is 1150 °C where the maximum d33 of 134 pC/N parallel to casting plane, the maximum k31 of 0.31, and the maximum Qm of 154 in perpendicular direction were obtained. 相似文献
3.
Bi2O3 was selected as liquid phase sintering aid to lower the sintering temperature of La(Mg0.5Ti0.5)O3 ceramics. The sintering temperature of La(Mg0.5Ti0.5)O3 ceramics is generally high, about 1600 °C. However, the sintering temperature was significantly lowered about 275 °C from 1600 °C to 1325 °C by incorporating in 15 mol% Bi2O3 and revealed the optimum microwave dielectric properties of dielectric constant (?r) value of 40.1, a quality factor (Q × f) value of 60,231 GHz, and the temperature coefficient (τf) value of 70.1 ppm/°C. During all addition ranges, the relative dielectric constants (?r) were different and ranged from 32.0 to 41.9, the quality factors (Q × f) were distributed in the range of 928–60,231 GHz, and the temperature coefficient (τf) varies from 0.3 ppm/°C to 70.3 ppm/°C. Noticeably, a nearly zero τf can be found for doping 5 mol% Bi2O3 sintering at 1325 °C. It implies that nearly zero τf can be achieved by appropriately adjusting the amount of Bi2O3 additions and sintering temperature for La(Mg0.5Ti0.5)O3 ceramics. 相似文献
4.
《Journal of the European Ceramic Society》2003,23(12):2163-2169
Textured bismuth titanate (Bi4Ti3O12) ceramics were fabricated by templated grain growth (TGG), using plate-like Bi4Ti3O12 particles prepared by a molten salt method as the templates. The templates were aligned in the fine-grained matrix by aqueous tape casting with their major surface parallel to the casting plane. Effect of sintering conditions on the grain orientation in the material was investigated. It was found that the degree of grain orientation (Lotgering factor, f) increased with the increase in sintering temperature, soaking time and heating rate. High Lotgering factor (f⩾0.92) can be obtained through careful control of the sintering parameters. The textured Bi4Ti3O12 ceramics showed a high anisotropy in its dielectric properties in the directions parallel and perpendicular to the casting plane. 相似文献
5.
The microwave dielectric properties of Sm(Mg0.5Ti0.5)O3 incorporated with various amount of Bi2O3 and B2O3 additives have been investigated systematically. In this study, both Bi2O3 and B2O3 additives acting as a sintering aid can effectively lower the sintering temperature from 1550 °C to 1300 °C. The ionic radius of Bi3+ for a coordination number of 6 is 0.103 nm, whereas the ionic radius of B3+ is 0.027 nm. Clearly, the ionic radius of Bi3+ is greatly larger than one of B3+, which resulted in the specimens incorporated with Bi2O3 having larger lattice parameters and cell volume than those incorporated with B2O3. The experimental results show that no second phase was observed throughout the entire experiments. Depending on the interfacial tension, the liquid phase may penetrate the grain boundaries completely, in which case the grains will be separated from one another by a thin layer as shown in Sm(Mg0.5Ti0.5)O3 ceramics incorporated with Bi2O3. Whereas, in Sm(Mg0.5Ti0.5)O3 ceramics incorporated with B2O3, the volume fraction of liquid is high, the grains may dissolve into the liquid phase, and rapidly rearrange, in which case contact points between agglomerates will be dissolved due to their higher solubility in the liquid, leading plate-like shape microstructure.A dielectric constant (?r) of 29.3, a high Q × f value of 26,335 GHz (at 8.84 GHz), and a τf of −32.5 ppm/°C can be obtained for Sm(Mg0.5Ti0.5)O3 ceramics incorporated with 10 mol% Bi2O3 sintered at 1300 °C. While Sm(Mg0.5Ti0.5)O3 ceramics incorporated with 5 mol% B2O3 can effectively lower temperature coefficient of resonant frequency, which value is −21.6 ppm/°C. The Sm(Mg0.5Ti0.5)O3 ceramic incorporated with heavily Bi2O3 and B2O3 additives exhibits a substantial reduction in temperature (∼250 °C) and compatible dielectric properties in comparison with that of an un-doped one. This implied that this ceramic is suitable for miniaturization in the application of dielectric resonators and filters by being appropriately incorporated with a sintering aid. 相似文献
6.
The microwave dielectric properties of La2.98/3Ba0.01(Mg0.5Sn0.5)O3 ceramics prepared by the conventional solid-state method were investigated for application in mobile communication. A 100 °C reduction of the sintering temperature was obtained by using CuO as a sintering aid. A dielectric constant of 20.0, a quality factor (Q × f) of 50,100 GHz and a temperature coefficient of resonant frequency τf of −78.3 ppm/°C were obtained when La2.98/3Ba0.01(Mg0.5Sn0.5)O3 ceramics with 0.25 wt.% CuO were sintered at 1500 °C for 4 h. 相似文献
7.
The influence of various sintering aids on the microwave dielectric properties and the structure of Nd(Mg0.5Ti0.5)O3 ceramics were investigated systematically. B2O3, Bi2O3, and V2O5 were selected as liquid-phase sintering aids to lower the sintering temperature. The sintered Nd(Mg0.5Ti0.5)O3 ceramics are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microwave dielectric properties. The sintering temperature of Nd(Mg0.5Ti0.5)O3 microwave dielectric ceramics is generally high, about 1500 °C. However, the sintering temperature was significantly lowered about 175 °C from 1500 °C to 1325 °C by incorporating in 10 mol% B2O3 and revealed the optimum microwave dielectric properties of dielectric constant (r) value of 26.2, a quality factor (Q × f) value of 61,307 (at 9.63 GHz), and τf value of −45.5 ppm/°C. NdVO4 secondary phase was observed at 10 mol% V2O5 addition in the sintering temperature range of 1300–1325 °C, which led the degradation in microwave dielectric properties. The microwave dielectric properties as well as grain sizes, grain morphology, and bulk density were greatly dependent on sintering temperature and various sintering aids. In this study, it is found that Nd(Mg0.5Ti0.5)O3 incorporated with 10 mol% B2O3 with lower sintering temperature and excellent dielectric microwave properties may be suggested for application in microwave communication devices. The use of liquid-phase sintering, the liquid formed during firing normally remains as a grain boundary phase on cooling. This grain boundary phase can cause a deterioration of the microwave properties. Therefore, the selection of a suitable sintering aid is extremely important. 相似文献
8.
M. Unruan N. Vittayakorn R. Wongmaneerung A. Prasatkhetragarn S. Ananta R. Yimnirun 《Ceramics International》2009
Pb(Co1/3Nb2/3)O3 (PCN) ceramics have been produced by sintering PCN powders synthesized from lead oxide (PbO) and cobalt niobate (CoNb2O6) with an effective method developed for minimizing the level of PbO loss during sintering. Attention has been focused on relationships between sintering conditions, phase formation, density, microstructural development, dielectric and ferroelectric properties of the sintered ceramics. From X-ray diffraction analysis, the optimum sintering temperature for the high purity PCN phase was found at approximately 1050 and 1100 °C. The densities of sintered PCN ceramics increased with increasing sintering temperature. However, it is also observed that at very high temperature the density began to decrease. PCN ceramic sintered at 1050 °C has small grain size with variation in grain shape. There is insignificant change of dielectric properties with sintering temperature. The P–E hysteresis loops observed at −70 °C are of slim-loop type with small remanent polarization values, which confirmed relaxor ferroelectric behavior of PCN ceramics. 相似文献
9.
Krishan KumarBinay Kumar 《Ceramics International》2012,38(2):1157-1165
Bi0.5(Na0.5K0.5)0.5TiO3 + y wt.% Nb (y = 0-1) piezoelectric ceramics were synthesized by solid state reaction. The effect of varying Nb concentration on various properties of BNKT ceramic has been investigated in detail. The effect of Nb-doping on dielectric and ferroelectric property has been presented. An increase in its depolarization temperature and Curie temperature with Nb concentration was observed. The electrical properties of pure and Nb-doped BNKT ceramic over a wide range of frequencies (20 Hz to 2 MHz) and temperature (30-430 °C) were studied using impedance spectroscopic technique. 相似文献
10.
Lead free piezoelectric Bi0.5(Na0.5K0.5)0.5TiO3 (pure and 1 wt.%, 2 wt.%, 4 wt.% Sb-doped) ceramics were synthesized away from its MPB. The crystalline nature of the BNKT ceramic was studied by XRD and SEM. Depolarization temperature (Td) and transition temperature (Tc) were observed through phase transitions in dielectric studies which were found to increase after Sb-doping, thus increasing its usable temperature range. In the study of relaxation behavior, the activation energy for relaxation was found to be 0.33, 0.43, 0.57 and 0.56 eV for pure and Sb-doped samples, respectively. All samples were found to exhibit normal Curie-Weiss law above their Tc. Doping of Sb was found to restrain the diffused character of the pure sample. In P-E loop, Sb-doping was found to increase the ferroelectric properties.Pure and Sb-doped BNKT ceramics exhibited high values of piezoelectric charge coefficient (d33) as 115, 121, 129 and 100 pC/N, respectively. 相似文献
11.
Nikolina Pavlovi?Vladimir Koval Jan DuszaVladimir V. Srdi? 《Ceramics International》2011,37(2):487-492
Effect of Ce and La substitution on the microstructure and dielectric properties of bismuth titanate (BT) ceramics was investigated. Bismuth titanate ceramics (Bi4−xAxTi3O12) (A = Ce or La; x = 0, 0.5, 1) were processed by sintering of pressed pellets, prepared from nanopowder synthesized by the modified sol-gel method. Pure and La modified bismuth titanate ceramics have single Bi4Ti3O12 phase of Aurivillius type, whereas a small amount of Bi2Ti2O7 pyrochlore phase appears in Ce modified bismuth titanate ceramics. In the same time addition of La and Ce improved sinterability of BT ceramics. The results of the measurement of dielectric constant and loss tangent at different frequencies (100 Hz-1 MHz) as a function of temperature reveal that Ce modified ceramics has a diffuse phase transition. Temperature Tm, corresponding to the maximum value of the dielectric constant, is shifted to higher temperature and the maximum value of the dielectric constant is decreased with increasing frequency, which indicate that relaxor behavior is caused by Ce substitution. 相似文献
12.
Doped hexagonal BaTiO3 (h-BaTiO3) ceramics have recently been identified as potential candidates for use in microwave dielectric resonators. However, similar to other common microwave ceramics, doped h-BaTiO3 ceramics require a sintering temperature higher than 1400 °C. In this study, the effects of Bi2O3 and Li2CO3 on the densification, microstructural evolution and microwave properties of hexagonal 12R-Ba(Ti0.5Mn0.5)O3 ceramics were examined. Results indicate that Bi2O3 and Li2CO3 are able to effectively reduce the sintering temperature of 12R-Ba(Ti05Mn0.5)O3 ceramics through liquid phase sintering while retaining the hexagonal structure and the microwave dielectric properties. The best results were obtained for the 12R-Ba(Ti0.5Mn0.5)O3 with the additions of 5 wt% Bi2O3 sintered at 1200 °C (?r: 36.0, Qfr: 6779 GHz, and τf: 25.3 ppm/°C), and 5 wt% Li2CO3 sintered at 1200 °C (?r: 28.1, Qfr: 5304 GHz, and τf: 35.3 ppm/°C). 相似文献
13.
14.
Ying-Chieh Lee Tai-Kuang LeeJhen-Hau Jan 《Journal of the European Ceramic Society》2011,31(16):3145-3152
This article studies the microstructure and piezoelectric properties of a ceramic lead-free NBT under different amount of ZnO doping. X-ray diffraction shows that Zn2+ diffuses into the lattice of (Bi0.5Na0.5)TiO3 to form a solid solution with a pure perovskite structure. By modifying the zinc oxide content, the sintering behavior of (Bi0.5Na0.5)TiO3 ceramics was significantly improved and the grain size was increased. The piezoelectric coefficient d33 for the 1.0 wt.% ZnO-doped (Bi0.5Na0.5)TiO3 ceramics sintered at 1050 °C was found to be 95 pC/N, and the electromechanical coupling factor kp = 0.13. However, the piezoelectric coefficient d33 for the 0.5 wt.% ZnO-doped (Bi0.5Na0.5)TiO3 ceramics sintered at 1140 °C was found to be 110 pC/N, and the electromechanical coupling factor kp = 0.17. 相似文献
15.
(1 − x)Ba0.4Sr0.6TiO3/xCaCu3Ti4O12 composite ceramics were prepared by spark plasma sintering. Sintering behavior, microstructures and dielectric properties of the composite ceramics were investigated by XRD, SEM, EDS and dielectric spectrometer. Dense composite ceramics consisting of Ba0.4Sr0.6TiO3 phase and CaCu3Ti4O12 phase were prepared at 800 °C for 0 min. The dielectric loss of the composite ceramic decreased with increasing amount of Ba0.4Sr0.6TiO3, and the high dielectric constant were retained. Moreover, the better temperature stability of dielectric constant was obtained. These improvements of dielectric characteristics have great scientific significance for potential application. 相似文献
16.
A new compound of barium bismuth neodymium titanate BaBi3.5Nd0.5Ti4O15 was synthesized using the traditional solid-state reaction method. X-ray diffraction analysis confirmed the compound to be a layered tetragonal structure and Raman spectrum indicated that Nd ions occupy the A site. The plate-like morphology with average grain size about 2–4 μm was observed by a scanning electron microscope (SEM). A precision impedance analyzer was used to measure the dielectric properties and impedance spectroscopy of the ceramics. The results show that the temperature of dielectric constant maximum (Tm), the room temperature dielectric constant (εr) and loss (tan δ) at 100 kHz are 287° C, 326 and 0.017, respectively. The modified Curie–Weiss law was used to describe the relaxor behavior of the ceramics which was attributed to the A site cationic disorder. The remnant polarization (2Pr) of the sample was observed to be 1.27 μC/cm2 at room temperature. 相似文献
17.
Energy-storage properties of [(Bi1/2Na1/2)0.94Ba0.06]La(1−x)ZrxTiO3 (BNT-BLZT, x=0, 0.02, 0.04, and 0.06) lead-free anti-ferroelectric ceramics fabricated via the conventional sintering technique were first investigated. Calculation from the X-ray diffraction results reveals that BNT-BLZT ceramic possesses a single perovskite structure phase. In addition, the P–E hysteresis loops measured at room temperature show that the BNT-BLZT (x=0.02) ceramics obtain the maximum P value of 37.5 μC/cm2 and the largest energy-storage density Wmax is 1.58 J/cm3. The temperature dependence of dielectric permittivity εr and dielectric loss tanδ illustrate that the addition of Zr can improve the piezoelectric properties of BT-BLZT ceramics. These properties indicate that BNT-BLZT ceramics might be a promising lead-free anti-ferroelectric material for energy storage application. 相似文献
18.
Eu-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT6-xEu, x=0.00–2.00 at%) lead-free piezoelectric ceramics have been synthesized by the solution combustion method. The effect of Eu doping concentration on the phase structure, microstructure and electrical properties of BNBT6 ceramics has been investigated. The XRD analysis confirms that the europium additive incorporates into the BNBT6 lattice and results in a phase transition from the coexistence of rhombohedral and tetragonal phases to a more symmetric pseudocubic phase. The SEM images indicate that the europium additive has little effect on the ceramic microstructure and the average grain size is about 2.0 μm. The electrical properties of BNBT6 ceramics can be improved by appropriate Eu doping. The 0.25 at% Eu doped BNBT6 ceramic presents excellent electrical properties: piezoelectric constant d33=149 pC/N, remnant polarization Pr=40.27 μC/cm2, coercive field Ec=2.95 kV/mm, dielectric constant εr=1658 and dissipation factor tan δ=0.0557 (10 kHz). 相似文献
19.
This study investigates the effects of copper oxide (CuO) addition, calcining temperature, and sintering temperature on the microstructure and the electrical properties (such as dielectric constant and loss tangent) of lead-free piezoelectric ceramic of bismuth sodium titanate (Bi0.5Na0.5TiO3), BNT, which was prepared using the mixed oxide method. Three kinds of starting powders (Bi2O3, Na2CO3 and TiO2) were mixed and calcined. This calcined BNT powder and a certain weight percentage of CuO were mixed, calcined, and compressed into a green compact of BNT-CuO. This green compact of BNT-CuO was sintered to be a disk doped with CuO, and its characteristics were measured. In this study, the calcining temperature ranged from 700 to 1000 °C, the sintering temperature ranged from 950 to 1050 °C, and the weight percentages of CuO doping included 2, 4, 6, and 8 wt.%. The largest relative density of the BNT-CuO disk obtained in this study was 96.7% at the calcining temperature of 700 °C, the sintering temperature of 950 °C, and 4 wt.% of CuO addition. The corresponding dielectric constant and loss tangent were 494 and 0.181%, respectively. This study shows that adding CuO to the BNT not only improves the relative density and the dielectric constant of the BNT disk, but it also lowers the sintering temperature. 相似文献
20.
Piezoelectric Bi0.5(Na0.82K0.18)0.5TiO3 thick films were prepared by aqueous gel-tape casting. Bi0.5(Na0.82K0.18)0.5TiO3 nano-powder with perovskite structure prepared by sol–gel process was obtained. The average particle size was 200 nm. A stable Bi0.5(Na0.82K0.18)0.5TiO3 suspension with 46 vol% solid loading and <1 Pa s viscosity was prepared when 0.8 wt% of ammonium polyacrylate was added with the pH value controlled in the range 7–9. The plasticizer glycerol had a positive effect on the fluidity of the suspensions. The tensile strength and strain to failure of the green tape were 0.42 MPa and 0.04 mm/mm when the addition of glycerol was 50 wt% of the premix solvent. The resulting about 100 μm thick films had relative permittivity of 910, dielectric loss of 4.9% at 10 kHz, remanent polarization of 24 μC/cm2, coercive field of 56 kV/cm, and longitudinal effective piezoelectric coefficient d33eff of 102 pC/N. The good performance illustrated that gel-tape casting was the effective way to prepare Bi0.5(Na0.82K0.18)0.5TiO3 thick film. 相似文献