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1.
Ferroelectric Glass-ceramics of the Na2O–BaO–Nb2O5–SiO2 system were obtained from controlled crystallization process performed on the parent glass of composition (24-x)Na2O-xBaO-26Nb2O5-50SiO2 where x?=?4 was selected. Nd2O3 doping was applied in the range 0–3 mol%. X-ray diffraction analysis indicated that NaNbO3 and NaBa2Nb5O15 crystals formed as two main crystalline phases. Their relative intensities varied with treatment temperature. Crystalline sizes of both NaNbO3 and NaBa2Nb5O15 calculated from XRD peak broadening were in nanoscale range. Increasing of doping content also gave a parent glass with higher bulk density. The dielectric constant measured at room temperature for glass-ceramic samples was found to be sensitive to the presence of NaBa2Nb5O15 phase. The results of the present work suggest that introduction of Nd3+ into Na2O-BaO-Nb2O5-SiO2 system not only alters the dielectric response but also changes the phase transition behaviors of the co-existant ferroelectric phases by suppressing the growth of the NaBa2Nb5O15 crystals. 相似文献
2.
采用类似溶胶-凝胶法合成稀土金属氧化物Dy2O3掺杂LiDyxMn2-xO4(x=0,0.01,0.02,0.05).通过XRD和恒流充放电测试了稀土金属元素Dy的掺杂对正极材料的结构以及电化学性能的影响.研究结果表明:当掺杂量x=0.02时,材料LiDy0.02Mn1.98O4具有较高的初始比容量(109mAh/g)和循环性能,50次循环后,容量保持率为95%. 相似文献
3.
R. K. Bhuyan T. Santhosh Kumar D. Goswami A. R. James D. Pamu 《Journal of Electroceramics》2013,31(1-2):48-54
Dielectric ceramics of Mg2TiO4 (MTO) were prepared by solid-state reaction method with 0.5–1.5 wt.% of La2O3 or V2O5 as sintering aid. The influences of La2O3 and V2O5 additives on the densification, microstructure and microwave dielectric properties of MTO ceramics were investigated. It is found that La2O3 and V2O5 additives lowered the sintering temperature of MTO ceramics to 1300 °C and 1250 °C respectively, whereas the pure MTO exhibits highest density at 1400 °C. The reduction in sintering temperature with these additives was attributed to the liquid phase effect. The average grain sizes of the MTO ceramics added with La2O3, and V2O5 found to decrease with an increase in wt%. The dielectric constant (εr) was not significantly changed, while unloaded Q values were affected with these additives, and the values were in the range of 92,000–157,550 GHz and 98,000–168,000 GHz with the addition of La2O3 and V2O5, respectively. The dielectric properties are strongly dependent on the densification and the microstructure of the MTO ceramics. The decrease in Q×f o value at higher concentration of La2O3 and V2O5 addition was owing to inhomogeneous grain growth and the liquid phase which is segregated at the grain boundary. In comparison with pure MTO ceramics, La2O3 and V2O5 additives effectively improved the densification and dielectric properties with lowering of sintering temperature. The proposed loss mechanisms suggest that the oxygen vacancies and the average grain sizes are the influencing factors in the dielectric loss of MTO ceramics. 相似文献
4.
采用液相共沉淀法制备了掺杂Bi_2O_3的锌酸钙粉末。X射线衍射测试表明,共沉淀的Bi没有进入锌酸钙的晶格而是以Bi_2O_3的形式析出并部分沉积在锌酸钙表面。恒电流充放电测试结果表明,Bi_2O_3在首次充电时能够转化为金属Bi并稳定存在于锌酸钙电极中。与未掺杂电极相比,掺杂10%(质量分数)Bi_2O_3后,锌酸钙电极的0.2 C比容量由391m Ah/g提高至433 m Ah/g,1 C比容量由372 m Ah/g提高至389 m Ah/g,3 C比容量由312 m Ah/g提高至330 m Ah/g,1 C循环30次后容量保持率由61%提高到92%。 相似文献
5.
The effects of CuO and TiO2 additives on the microstructure and microwave dielectric properties of Al2O3 ceramics were investigated. Al2O3 ceramics with CuO and TiO2 additions can be well sintered to achieve 93∼98% theoretical densities below 1,360 °C due to Ti4Cu2O liquid phase sintering effect. The Qf values decreased with increasing CuO and TiO2 content, due to the formation of the second phase Ti4Cu2O. However, the varying behaviors of the dielectric constant (ɛ
r
) and temperature coefficients (τ
f
) were associated with phase constitutions, as a result of the change of CuO and TiO2content. The τ
f
can be shifted close to 0 ppm/°C by controlling the content of CuO and TiO2. The specimens with 0.5 wt.% CuO and 7 wt.% TiO2 sintered at 1,360 °C for 4 h showed ɛ
r
of 11.8, Qf value of 30,000 GHz, and τ
f
of −7 ppm/°C. 相似文献
6.
采用金相观察、X衍射(XRD)、扫描电镜(SEM)、结合能谱(EDS)研究了分级退火工艺对镁合金显微组织、相结构、表面形貌及成分分布的影响;采用化学浸泡和电化学方法研究了该镁合金在质量分数为3.5%NaCl溶液中腐蚀行为和电化学性能.结果表明,热处理可以改变镁合金的组织结构和成分分布,进而影响镁合金的电极电位和自腐蚀速度,经350℃分级退火工艺得到的镁合金晶粒尺寸均匀细致、成分分布均匀.在晶界形成Mg2Sn、Mg2Pb和Ga2Mg5网状的疏松多孔相,使镁合金负极的工作电极电位负而且稳定,自腐蚀速度很低且腐蚀产物更易于剥离从而促进电池反应深入进行. 相似文献
7.
Polycrystalline Y-type hexagonal ferrite, with composition of Ba2?x Bi x Zn0.8Co0.8+x Cu0.4Fe12?x O22 (x?=?0~0.4), was prepared by the solid state reaction method. The effect of Bi substitution on phase formation, sintering process and magnetic properties were investigated in detail. The phase formation process was characterized by the means of powder X-ray diffraction (XRD). Bi3+ can substitute Ba2+ in Y-type hexagonal ferrite as divalent metal ion Co2+ substitute Fe3+ at the same time for electrovalence balance. As Bi amount is less than 0.3, the phase formation of Y-type hexagonal ferrite will not be destroyed. As Bi amount further increases, the lattice mismatch induced by the difference in ionic radii of Bi3+ and Ba2+ ions prevents the formation of pure Y-type phase. The samples with proper Bi substitution (0.05?<?x?<?0.3) have much lower phase formation temperature than that of the samples without Bi substitution. Bi substitution can also promote the sintering process. As x?>?0.1, the samples can be sintered well under 900 °C without any other addition. These materials are suitable for multilayer chip inductive components and devices. 相似文献
8.
In this study, to develop the optimal composition of ceramics for low loss piezoelectric actuator and ultrasonic motor applications, (K0.5Na0.5)(Nb0.97Sb0.03)O3?+?0.009 K5.4Cu1.3Ta10O29?+?0.1wt%Li2CO3?+?xwt%Bi2O3(x?=?0?~?0.9) lead-free piezoelectric ceramics with a fixed quantity of 0.009 K5.4Cu1.3Ta10O29 (abbreviated as KCT) were manufactured using the conventional solid-state solution processes. The effects of Bi2O3 addition on the dielectric and piezoelectric properties were then investigated. From the X-ray diffraction analysis result the specimens demonstrated orthorhombic symmetry when Bi2O3 was less 0.6?wt%, a pseudo-cubic phase appeared when Bi2O3 was 0.9?wt%. SEM images indicate that a small amount of Bi2O3 addition affect the microstructure. The piezoelectric properties of (K0.5Na0.5)(Nb0.97Sb0.03)O3 ceramics were greatly improved by a certain amount of Bi2O3 addition. Excellent properties of density?=?4.54?g/cm3, relative densities?=?98.5?%, k p?=?0.468, Q m?=?1,715 and d 33?=?183 pC/N were obtained with a composition of 0.3?wt% Bi2O3 相似文献
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11.
Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 with B2O3 and CuO additions 总被引:1,自引:0,他引:1
Jeong-Ryeol Kim Dong-Wan Kim Sung Hun Yoon Kug Sun Hong 《Journal of Electroceramics》2006,17(2-4):439-443
The low sintering temperature and the good dielectric properties such as high dielectric constant (ε
r
), high quality factor (Q × f), and small temperature coefficient of resonant frequency (TCF) are required for the application of chip passive components
in wireless communication low temperature co-fired ceramics (LTCC). In the present study, the sintering behaviors and dielectric
properties of Ba3Ti5Nb6O28 ceramics were investigated as a function of B2O3-CuO content. The pure Ba3Ti5Nb6O28 system showed a high sintering temperature (1250∘C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ε
r
of 37, TCF of −12 ppm/∘C. The addition of B2O3-CuO was revealed to lower the sintering temperature of Ba3Ti5Nb6O28, 900∘C and to enhance the microwave dielectric properties: Q × f of 32,500 GHz, ε
r
of 40, TCF of 9 ppm/∘C. From the X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) studies, these phenomena were explained
in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties. 相似文献
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13.
Jong-Bong Lim Sahn Nahm Hyo-Tae Kim Jong-Hee Kim Jong-Hoo Paik Hwack-Joo Lee 《Journal of Electroceramics》2006,17(2-4):393-397
The effect of B2O3 and CuO on the sintering temperature and microwave dielectric properties of BaTi4O9 ceramics was investigated. The BaTi4O9 ceramics were able to be sintered at 975∘C when B2O3 was added. This decrease in the sintering temperature of the BaTi4O9 ceramics upon the addition of B2O3 is attributed to the formation of BaB2O4 second phase whose melting temperature is around 900∘C. The B2O3 added BaTi4O9 ceramics alone were not sintered below 975∘C, but were sintered at 875∘C when CuO was added. The formation of BaCu(B2O5) second phase could be responsible for the decrease in the sintering temperature of the CuO and B2O3 added BaTi4O9 ceramics. The BaTi4O9 ceramics containing 2.0 mol% B2O3 and 5.0 mol% CuO sintered at 900∘C for 2 h have good microwave dielectric properties of εr = 36.3, Q× f = 30,500 GHz and τf = 28.1 ppm/∘C 相似文献
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15.
采用SEM、XRD分析和锂离子电池性能测试,研究了Co3O4的化学和物理性能及微观形貌对合成LiCoO2的微观形貌、电化学性能的影响.通过改变烧制工艺,LiCoO2电池的比容量从128 mAh/g提高到139 mAh/g以上,100次循环容量衰减在15%以下,电压平台衰减不到17%,其电化学性能与进口原料相当. 相似文献
16.
The Influence of Bi2O3 and Sb2O3 on the Electrical Properties of ZnO-Based Varistors 总被引:1,自引:0,他引:1
J. Ott A. Lorenz M. Harrer E.A. Preissner C. Hesse A. Feltz A.H. Whitehead M. Schreiber 《Journal of Electroceramics》2001,6(2):135-146
This work presents a study of the influence of both Bi content and Sb/Bi ratio on the electrical characteristics of a commercial-type ZnO varistor. In contrast to previous studies two nonlinear coefficients, the breakdown fields and energy absorption abilities were measured after sintering at 970°C or 930°C. The Bi-content was varied from 0.9 to 1.8 at% while the Sb/Bi ratio was varied from 0.8 to 1.5, leading to values of up to 104 for the nonlinear coefficient 1, 1100 V mm–1 for the breakdown field and 1137 J cm–3 for the energy absorption ability. The highest value was measured for the highest Bi-content and the lowest Sb/Bi ratio and vice versa. The breakdown field E
V increased with lower sintering temperature, increased Sb/Bi ratio (at a given Bi-content) and increased Bi-content (at a given Sb/Bi ratio). The energy absorption coefficient increased at the higher sinter temperature and with lower Sb and Bi concentrations.The observed effects were related to the amount of spinel phase (Zn7Sb2O12) formed during the sintering process and the amount of liquid phase present during early stages of the sintering process. 相似文献
17.
(1-x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 (BNT-xPT, 0.42????x????0.52) ceramics were prepared by the conventional mixed oxide method. With the increase of PT content, a change from rhombohedral phase to tetragonal phases, and while the morphotropic phase boundary (MPB) composition is located in the range of x?=?0.46?C0.48. For x?=?0.46 sample, it exhibited a high Curie temperature (T c) of 410?°C and good piezoelectric properties, d 33 ~230pC/N, k p ~40?% and k t ~22?%. For 0.46????x????0.50 samples, it can be found that depolarization temperature is around 350?°C by thermal depoling method. 相似文献
18.
采用氧化物陶瓷工艺制备低温共烧铁氧体(LTCF)多层片式器件用NiCuZn铁氧体材料,研究了V_2O_5掺杂对材料微观结构、磁导率及其温度特性的影响。结果表明,随V_2O_5掺杂量的增加,样品平均晶粒尺寸增大,材料烧结温度降低,磁导率先增大后降低;宽温NiCuZn铁氧体配方采用0.4wt%的V_2O_5掺杂,可使材料实现低温烧成(烧结温度900℃左右),并具有高磁导率(500左右)、致密的细晶粒显微结构,从而获得满足LTCF多层片式铁氧体器件高、低温应用环境(-55~+85℃)下磁性能要求的低温烧结NiCuZn铁氧体宽温材料。 相似文献
19.
20.
Binod Kumar Singh Hojin Ryu Chang‐Hae Kim Ha‐Kyun Jung Jung‐Kyu Park Kyeung‐Yeol Jung Ho‐Jung Chang 《IEEJ Transactions on Electrical and Electronic Engineering》2006,1(1):30-34
Phosphor powders of zinc gallate (ZnGa2O4) with Mg and Mn for green and Tm‐Mg for blue luminescence were prepared by solid state reaction method for their improved luminescent properties. Green‐luminescence emitting ZnMnGa2O4 reached maximum intensity at Mn = 0.005 mol% and further improvement was achieved by the addition of Mg2+. Tm‐Mg based zinc gallate phosphor exhibited a strong blue emission, centered at ∼420 nm with the maximum intensity achieved for 0.003 mol% of Mg and 0.015 mol% of Tm. This study established the possibilities of controlling the luminescent characteristics of zinc gallate by adding various elements. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献