共查询到20条相似文献,搜索用时 31 毫秒
1.
Yuan-Bin Chen 《Journal of Alloys and Compounds》2011,509(24):6884-6888
The effects of BaCu(B2O5) additives on the sintering temperature and microwave dielectric properties of (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics were investigated. The (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics were not able to be sintered below 1000 °C. However, when BaCu(B2O5) were added, they were sintered below 1000 °C and had the good microwave dielectric properties. It was suggested that a liquid phase with the composition of BaCu(B2O5) was formed during the sintering and assisted the densification of the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics at low temperature. BaCu(B2O5) powders were produced and used to reduce the sintering temperature of the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics. Good microwave dielectric properties of Q × f = 35,000 GHz, ?r = 18.5.0 and τf = −51 ppm/°C were obtained for the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics containing 7 wt.% mol% BaCu(B2O5) sintered at 950 °C for 4 h. 相似文献
2.
Piezoelectric and dielectric properties of Dy2O3-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics
Chen Zhi-hui Ding Jian-ning Mei LinYuan Ning-yi Zhu Yuan-yuan 《Journal of Alloys and Compounds》2011,509(2):482-485
(Bi0.5Na0.5)0.94Ba0.06TiO3 + x wt% Dy2O3 with x = 0-0.3 ceramics were synthesized by conventional solid-state processes. The effects of Dy2O3 on the microstructure, the piezoelectric and dielectric properties were investigated. X-ray diffraction pattern confirmed that the coexistence of tetragonal and rhombohedral phases in the (Bi0.5Na0.5)0.94Ba0.06TiO3 composition was not changed by adding 0.05-0.3 wt% Dy2O3. SEM images indicate that all the ceramics have pore-free microstructures with high density, and that doping of Dy2O3 inhibits the grain growth of the ceramics. The addition of Dy2O3 shows the double effects on decreasing the piezoelectric and dielectric properties for 0 < x < 0.15 when Dy3+ ions substitute B-site Ti4+ ions, and increasing the properties for 0.15 < x < 0.3 when Dy3+ ions enters into A-site of the perovskite structure. The optimum electric properties of piezoelectric constant d33 = 170 pC/N and the dielectric constant ?r = 1900 (at a frequency of 1 kHz) are obtained at x = 0.3. 相似文献
3.
Minghui ZhangHong Wang Haibo YangXinguang Wu Weihong LiuXi Yao 《Journal of Alloys and Compounds》2011,509(38):L344
Screen printed Ba0.6Sr0.4TiO3 (BST6/4) thick films were fabricated by reactive sintering at a low temperature below 900 °C. The dielectric properties in radio frequency range were measured on samples of sandwich structure MIM capacitors by impedance analyzer, while that in microwave frequency range were measured on samples of thick films without top and bottom electrodes by split-post dielectric resonator method. The thick films exhibited a low permittivity, while at the same time, maintained a high tunability. The permittivity and dielectric loss at 1 MHz were 228.8 and 0.007, respectively. The corresponding values measured at 9.9 GHz were 82.24 and 0.109, respectively. The tunability was as high as 72.4% (150 kV/cm, 10 kHz). This method provides a simple and effective route to obtain thick films with great potential in applications in Low Temperature Co-fired Ceramic (LTCC) and microwave tunable devices. 相似文献
4.
以0.2 mol/L Ba(OH)2+0.2 mol/L Sr(OH)2溶液为电解液,采用微弧氧化法,在Ti板表面原位生长铁电薄膜,并对薄膜的物相构成、元素分布情况、截面结构及介电性能进行表征。结果表明:该工艺下制备的薄膜主要由四方相Ba0.5Sr0.5TiO3构成,薄膜致密层内,Ba,Sr,Ti和O元素分布都较均匀,但在微弧氧化孔洞附近存在含量波动;该薄膜在1 kHz下的介电常数较优,为411.3。最后对微弧氧化沉积铁电薄膜的成膜过程进行了分析,提出了微弧氧化过程中可能存在的化学反应。 相似文献
5.
Jhih-Yong ChenCheng-Liang Huang 《Journal of Alloys and Compounds》2011,509(2):426-430
The crystal structure and the dielectric properties of (1 − x)La(Mg0.5Ti0.5)O3-xCa0.8Sm0.4/3TiO3 ceramics have been investigated. Ca0.8Sm0.4/3TiO3 was employed as a τf compensator and was added to La(Mg0.5Ti0.5)O3 to achieve a temperature-stable material. The formation of (1 − x)La(Mg0.5Ti0.5)O3-xCa0.8Sm0.4/3TiO3 solid solutions were confirmed by the XRD results and the measured lattice parameters for all compositions. The dielectric properties are strongly correlated to the sintering temperature and the compositional ratio of the specimens. Although the ?r of the specimen could be boosted by increasing the amount of Ca0.8Sm0.4/3TiO3, it would instead render a decrease in the Q × f. The τf value is strongly correlated to the compositions and can be controlled by the existing phases. A new microwave dielectric material 0.45La(Mg0.5Ti0.5)O3-0.55Ca0.8Sm0.4/3TiO3, possessing a fine combination of microwave dielectric properties with an ?r of 47.83, a Q × f of 26,500 GHz (at 6.2 GHz) and a τf of −1.7 ppm/°C, is proposed as a very promising candidate material for today's 3G applications. 相似文献
6.
Microwave dielectric properties and microstructures of (Mg0.95Co0.05)TiO3 ceramics prepared by a new sintering method (reaction-sintering method) were investigated. A pure phase of (Mg0.95Co0.05)TiO3 was obtained by the new method and excellent dielectric properties were observed due to uniformities of the microstructure and the phase. In contrast, the secondary phase (Mg0.95Co0.05)Ti2O5 was observed in samples prepared by conventional sintering method. In order to study the influence of secondary phase on the microwave dielectric properties quantitatively, the weight fraction of (Mg0.95Co0.05)Ti2O5 was calculated on the basis of Rietveld refinement. The pore-free?r values of specimens prepared by two different methods indicated that porosity plays an important role in the ?r values of (Mg0.95Co0.05)TiO3 ceramics. Specimens sintered by reaction-sintering method at 1350 °C for 4 h possess excellent dielectric properties with an ?r of 16.3, a Q × f value of 244,500 GHz, and a τf value of −53.5 ppm/°C. 相似文献
7.
The phases, microstructure and microwave dielectric properties of ZnTiNb2O8-xTiO2 composite ceramics with different weight percentages of BaCu(B2O5) additive prepared by solid-state reaction method have been investigated using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that the microwave dielectric properties were strongly dependent on densification, grain sizes and crystalline phases. The sintering temperature of ZnTiNb2O8 ceramics was reduced from 1250 °C to 950 °C by doping BaCu(B2O5) additive and the temperature coefficient of resonant frequency (τf) was adjusted from negative value of −52 ppm/°C to 0 ppm/°C by incorporating TiO2. Addition of 2 wt% BaCu(B2O5) in ZnTiNb2O8-xTiO2 (x = 0.8) ceramics sintered at 950 °C showed excellent dielectric properties of ?r = 38.89, Q × f = 14,500 GHz (f = 4.715 GHz) and τf = 0 ppm/°C, which represented very promising candidates as LTCC dielectrics for LTCC applications. 相似文献
8.
Yuan-Bin Chen 《Journal of Alloys and Compounds》2011,509(21):6285-6288
The crystal structures, phase compositions and the microwave dielectric properties of the xLa(Mg1/2Ti1/2)O3-(1 − x)Ca0.8Sr0.2TiO3 composites prepared by the conventional solid state route have been investigated. The formation of solid solution is confirmed by the XRD patterns. Doping with B2O3 (0.5 wt.%) can effectively promote the densification and the dielectric properties of xNd(Mg1/2Ti1/2)O3-(1 − x)Ca0.6La0.8/3TiO3 ceramics. It is found that xNd(Mg1/2Ti1/2)O3-(1 − x)Ca0.6La0.8/3TiO3 ceramics can be sintered at 1375 °C, due to the liquid phase effect of B2O3 addition observed by Scanning Electronic Microscopy. At 1375 °C, 0.4Nd(Mg1/2Ti1/2)O3-0.6Ca0.6La0.8/3TiO3 ceramics with 1 wt.% B2O3 addition possesses a dielectric constant (?r) of 49, a Q × f value of 13,000 (at 8 GHz) and a temperature coefficients of resonant frequency (τf) of 1 ppm/°C. As the content of Nd(Mg1/2Ti1/2)O3 increases, the highest Q × f value of 20,000 GHz for x = 0.9 is achieved at the sintering temperature 1400 °C. 相似文献
9.
Yih-Chien Chen Sheng-Kai YangKuang-Chiung Chang 《Journal of Alloys and Compounds》2011,509(39):9518-9522
The microwave dielectric properties of La(Mg0.5−xNixSn0.5)O3 ceramics were examined with a view to their exploitation for mobile communication. The La(Mg0.5−xNixSn0.5)O3 ceramics were prepared by the conventional solid-state method at various sintering temperatures. The X-ray diffraction patterns of the La(Mg0.4Ni0.1Sn0.5)O3 ceramics revealed no significant variation of phase with sintering temperatures. Apparent density of 6.71 g/cm3, dielectric constant (?r) of 20.19, quality factor (Q × f) of 74,600 GHz, and temperature coefficient of resonant frequency (τf) of −85 ppm/°C were obtained for La(Mg0.4Ni0.1Sn0.5)O3 ceramics that were sintered at 1550 °C for 4 h. 相似文献
10.
A. Chaouchi S. KennourS. d’Astorg M. Rguiti C. Courtois S. MarinelM. Aliouat 《Journal of Alloys and Compounds》2011,509(37):9138-9143
The crystal structure, microstructure, dielectric and ferroelectric properties of (1 − x)Na0.5Bi0.5TiO3-xBaTiO3 ceramics with x = 0, 0.03, 0.05, 0.07 and 0.1 are investigated. A structural variation according to the system composition was investigated by X-ray diffraction (XRD) analyses. The results revealed that the synthesis temperature for pure perovskite phase powder prepared by the present sol-gel process is much lower (800 °C), and a rhombohedral-tetragonal morphotropic phase boundary (MPB) is found for x = 0.07 composition which showing the highest remanent polarization value and the smallest coercive field. The optimum dielectric and piezoelectric properties were found with the 0.93Na0.5Bi0.5TiO3-0.07BaTiO3 composition. The piezoelectric constant d33 is 120 pC/N and good polarization behaviour was observed with remanent polarization (Pr) of 12.18 pC/cm2, coercive field (Ec) of 2.11 kV/mm, and enhanced dielectric properties ?r > 1500 at room temperature. The 0.93Na0.5Bi0.5TiO3-0.07BaTiO3-based ceramic is a promising lead-free piezoelectric candidate for applications in different devices. 相似文献
11.
This study investigated the potential applications of microwave dielectric properties of Mg2SnO4 ceramics in mobile communication. Mg2SnO4 ceramics were prepared using a conventional solid-state method. The X-ray diffraction patterns of the Mg2SnO4 ceramics revealed no significant variation of phase with sintering temperature. A maximum density of 4.62 g/cm3, a dielectric constant (?r) of 8.41, a quality factor (Q × f) of 55,100 GHz, and a temperature coefficient of resonant frequency (τf) of −62 ppm/ °C were obtained when Mg2SnO4 ceramics were sintered at 1550 °C for 4 h. 相似文献
12.
Pure and Pr6O11-doped CaCu3Ti4O12 (CCTO) ceramics were prepared by conventional solid-state reaction method. The compositions and structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of Pr-ion concentration on dielectric properties of CCTO were measured in the ranges of 60 Hz-3 MHz and 290-490 K. The third phase of Ca2CuO3 was observed from the XRD of CCTO ceramics. From SEM, the grain size was decreased obviously with high valence Pr-ion (mixing valence of Pr3+ and Pr4+) substituting Ca2+. The room temperature dielectric constant of Pr-doped CCTO ceramics, sintered at 1323 K, was an order of magnitude lower than the pure CCTO ceramics due to the grain size decreasing and Schottky potential increasing. The dielectric spectra of Pr-doped CCTO were flatter than that of pure CCTO. The loss tangent of Pr-doped CCTO ceramics was less than 0.20 in 2 × 102-105 Hz region below 440 K. The complex impedance spectra of pure and Pr-doped CCTOs were fitted by ZView. From low to high frequency, three semicircles were observed corresponding to three different conducting regions: electrode interface, grain boundary and grain. By fitting the resistors R and capacitors C, the activation energies of grain boundary and electrode contact were calculated. All doped CCTOs showed higher activation energies of grain boundary and electrode than those of pure CCTO ceramics, which were concordant with the decreasing of dielectric constant after Pr6O11 doping. 相似文献
13.
Prasit Thongbai Bundit PutasaengTeerapon Yamwong Santi Maensiri 《Journal of Alloys and Compounds》2011,509(27):7416-7420
Non-ohmic and dielectric properties of Ca2Cu2Ti4O12 (CaCu3Ti4O12/CaTiO3 composite) ceramics prepared by a polymer pyrolysis method (PP-ceramic samples) are investigated. The PP-ceramics show a highly dense structure and improved non-ohmic and dielectric properties compared to the ceramics obtained by a solid state reaction method (SSR-ceramic samples). ?′ (tan δ) of the PP-ceramic samples is found to be higher (lower) than that of the SSR-ceramic samples. Interestingly, the PP-ceramic sintered at 1050 °C for 10 h exhibits the high ?′ of 2530 with weak frequency dependence below 1 MHz, the low tan δ less than 0.05 in the frequency range of 160 Hz-177 kHz, and the little temperature coefficient, i.e., |Δ?′| ≤ 15 % in the temperature range from −55 to 85 °C. These results indicate that the CaCu3Ti4O12/CaTiO3 composite system prepared by PP method is a promising high-?′ material for practical capacitor application. 相似文献
14.
Zhai JiweiH. Chen C.C. ChouS.I. Raevskaya S.A. Prosandeev I.P. Raevski 《Journal of Alloys and Compounds》2011,509(20):6113-6116
Study of the dielectric tunability and susceptibility, in a wide temperature range and at different bias fields, in Ba0.6Sr0.4TiO3 (BST) sol-gel derived ceramics of different crystallite sizes (between 1 and 6 μm), establishes two new regularities. The first one concerns the relative temperature of the maxima positions of the tunability and susceptibility. We show that the maximum in tunability is always at lower temperatures compared to the maximum in susceptibility. The second regularity tells that the electric field dependence of the susceptibility maximum temperature is always stronger than the one for the tunability maximum temperature. In small-size crystallite BST ceramics the temperature of susceptibility maximum starts changing only above a certain threshold field. Additionally, we discuss the nature of an extrinsic contribution to tunability in small-size crystallite BST ceramics. 相似文献
15.
(1 − x)ZnMoO4-xTiO2 (x = 0.0, 0.05, 0.158, 0.25, and 0.35) composite ceramics were synthesized by the conventional solid state reaction process. The sintering behavior, phase composition, chemical compatibility with silver, and microwave dielectric properties were investigated. All the specimens can be well densified below 950 °C. From the X-ray diffraction analysis, it indicates that the triclinic wolframite ZnMoO4 phase coexists with the tetragonal rutile TiO2 phase, and it is easy for silver to react with ZnMoO4 to form Ag2Zn2(MoO4)3 phase and hard to react with TiO2. When the volume fraction of TiO2 (x value) increasing from 0 to 0.35, the microwave dielectric permittivity of the (1 − x)ZnMoO4-xTiO2 composite ceramics increases from 8.0 to 25.2, the Qf value changes in the range of 32,300-43,300 GHz, and the temperature coefficient τf value varies from −128.9 to 157.4 ppm/°C. At x = 0.158, the mixture exhibits good microwave dielectric properties with a ?r = 13.9, a Qf = 40,400 GHz, and a τf = +2.0 ppm/°C. 相似文献
16.
The microwave dielectric properties and microstructures of (1 − x)La(Mg0.5Ti0.5)O3-x(Ca0.8Sr0.2)TiO3 ceramics, prepared by a mixed oxide route, have been investigated. The forming of solid solutions was confirmed by the XRD patterns and the measured lattice parameters for all compositions. A near zero τf was achieved for samples with x = 0.5, although the dielectric properties varied with sintering temperature. The Q × f value of 0.5La(Mg0.5Ti0.5)O3-0.5(Ca0.8Sr0.2)TiO3 increased up to 1475 °C, after which it decreased. The decrease in dielectric properties was coincident with the onset of rapid grain growth. The optimum combination of microwave dielectric properties was achieved at 1475 °C for samples where x = 0.5 with a dielectric constant ?r of 47.12, a Q × f value of 35,000 GHz (measured at 6.2 GHz) and a τf value of −4.7 ppm/°C. 相似文献
17.
Yanyan HeYebin Xu Ting LiuChunlian Zeng Wanping Chen 《Journal of Alloys and Compounds》2011,509(3):904-908
BaZr0.2Ti0.8O3-Mg2SiO4-MgO composites were prepared by a solid-state reaction method, and their dielectric and tunable characteristics were investigated for the potential application as microwave tunable materials. It is observed that the addition of Mg2SiO4-MgO into BaZr0.2Ti0.8O3 form ferroelectric (BaZr0.2Ti0.8O3)-dielectric (Mg2SiO4-MgO) composites. The dielectric constant and loss tangent of BaZr0.2Ti0.8O3-Mg2SiO4-MgO composites have been reduced and the overall tunability is maintained at a sufficiently high level. An anomalous relation between dielectric constant and tunability was observed: with the increase of Mg2SiO4 content (>30 wt%), the dielectric constant of composite decreases and the tunability increases. The anomalous increased tunability can be attributed to redistribution of the electric field. BaZr0.2Ti0.8O3-Mg2SiO4-MgO composites have tunability of 14.2-17.9% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring low dielectric constant. 相似文献
18.
The microwave dielectric properties and the microstructures of the (1 − x)(Mg0.6Zn0.4)0.95Co0.05TiO3–xCa0.61Nd0.26TiO3 ceramic system were investigated. In order to achieve a temperature-stable material, we studied a method of combining a positive temperature coefficient material with a negative one. Ca0.61Nd0.26TiO3 has a large positive temperature coefficient of resonant frequency. (Mg0.6Zn0.4)0.95Co0.05TiO3 possesses a negative temperature coefficient of resonant frequency. By appropriately adjusting the x value in the (1 − x)(Mg0.6Zn0.4)0.95Co0.05TiO3–xCa0.61Nd0.26TiO3 ceramic system, a near-zero τf value can be obtained. A new microwave dielectric material of 0.8(Mg0.6Zn0.4)0.95Co0.05TiO3–0.2Ca0.61Nd0.26TiO3 possesses the excellent dielectric properties of a dielectric constant of 28.6, a Q × f value of 80,600 GHz and a temperature coefficient of resonant frequency of 4.1 ppm/°C and has a lower sintering temperature of 1250 °C. 相似文献
19.
Phase evolution and microwave dielectric properties of (1 − x)(Mg0.95Co0.05)2TiO4-xTiO2 (x = 0-1) ceramics prepared by the conventional mixed oxide route have been investigated. Increasing the TiO2 content would lead to a main phase transformation from (Mg0.95Co0.05)2TiO4 to (Mg0.95Co0.05)TiO3, (Mg0.95Co0.05)Ti2O5 and then TiO2. Not only did the TiO2 addition compensate the τf, it also lowered the sintering temperature of specimen. A huge drop of Q × f occurs at a 40-60 mol% TiO2 addition was attributed to the formation of (Mg0.95Co0.05)Ti2O5 phase. Specimen with x = 0.78 can possess an excellent combination of microwave dielectric properties: ?r ∼ 24.77, Q × f ∼ 38,500 GHz and τf ∼ −1.3 ppm/°C. 相似文献
20.
Haimin NiLaihui Luo Weiping LiYuejin Zhu Haosu Luo 《Journal of Alloys and Compounds》2011,509(9):3958-3962
Lead-free (1 − x)Bi0.47Na0.47Ba0.06TiO3-xKNbO3 (BNBT-xKN, x = 0-0.08) ceramics were prepared by ordinary ceramic sintering technique. The piezoelectric, dielectric and ferroelectric properties of the ceramics are investigated and discussed. The results of X-ray diffraction (XRD) indicate that KNbO3 (KN) has diffused into Bi0.47Na0.47Ba0.06TiO3 (BNBT) lattices to form a solid solution with a pure perovskite structure. Moderate additive of KN (x ≤ 0.02) in BNBT-xKN ceramics enhance their piezoelectric and ferroelectric properties. Three dielectric anomaly peaks are observed in BNBT-0.00KN, BNBT-0.01KN and BNBT-0.02KN ceramics. With the increment of KN in BNBT-xKN ceramics, the dielectric anomaly peaks shift to lower temperature. BNBT-0.01KN ceramic exhibits excellent piezoelectric properties and strong ferroelectricity: piezoelectric coefficient, d33 = 195 pC/N; electromechanical coupling factor, kt = 58.9 and kp = 29.3%; mechanical quality factor, Qm = 113; remnant polarization, Pr = 41.8 μC/cm2; coercive field, Ec = 19.5 kV/cm. 相似文献