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1.
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
2.
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
3.
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
4.
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
5.
Xiuli ChenHuanfu Zhou Liang FangXiaobin Liu Yiliang Wang 《Journal of Alloys and Compounds》2011,509(19):5829-5832
The effects of BaCu(B2O5) (BCB) additions on the sintering temperature and microwave dielectric properties of Li2MgTi3O8 ceramic have been investigated. The pure Li2MgTi3O8 ceramic shows a relative high sintering temperature (∼1000 °C) and good microwave dielectric properties as Q × f of 40,000 GHz, ?r of 27.2, τf of 2.6 ppm/°C. It was found that the addition of a small amount of BCB can effectively lower the sintering temperature of Li2MgTi3O8 ceramics from 1025 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 0.5 wt% BCB added Li2MgTi3O8 ceramic sintered at 900 °C for 2 h exhibited good microwave dielectric properties of Q × f = 36,200 GHz (f = 7.31 GHz), ?r = 26 and τf = −2 ppm/°C. Compatibility with Ag electrode indicates this material can be applied to low temperature-cofired ceramics (LTCC) devices. 相似文献
6.
Yuan-Bin Chen 《Journal of Alloys and Compounds》2011,509(3):1050-1053
Ceramics in the system La(Mg1−xZnx)1/2Ti1/2O3 with B2O3 additions (1 wt.%) have been investigated by the conventional solid-state route. The XRD patterns of the sintered samples (0.3 ≤ x ≤ 1.0) revealed single phase formation with a structure. The unit cell volume slightly increased with increasing Zn content (x). La(Mg1−xZnx)1/2Ti1/2O3 were found to form perovskite solid solutions in the whole compositional range. The maximum values of the dielectric constant and the quality factor multiples resonant frequency (Q × f) can be obtained when the La(Mg0.7Zn0.3)1/2Ti1/2O3 with 0.5 wt.% B2O3 additive were sintered at 1475 °C for 4 h. The temperature coefficient of resonant frequency τf (−63 ppm/°C) was measured for x = 0.7. 相似文献
7.
In this work, we report on the Pb(Mg1/3Nb2/3)O3-Pb(Zn1/3Nb2/3)O3-Pb(Zr0.52Ti0.48)O3 (PMN-PZN-PZT) ceramics with Ba(W0.5Cu0.5)O3 as the sintering aid that was manufactured in order to develop the low-temperature sintering materials for piezoelectric device applications. The phase transition, microstructure, dielectric, piezoelectric properties, and the temperature stability of the ceramics were investigated. The results showed that the addition of Ba(W0.5Cu0.5)O3 significantly improved the sintering temperature of PMN-PZN-PZT ceramics and could lower the sintering temperature from 1005 to 920 °C. Besides, the obtained Ba(W0.5Cu0.5)O3-doped ceramics sintered at 920 °C have optimized electrical properties, which are listed as follows: (Kp = 0.63, Qm = 1415 and d33 = 351 pC/N), and high depolarization temperature above 320 °C. These results indicated that this material was a promising candidate for high-power multilayer piezoelectric device applications. 相似文献
8.
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
9.
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
10.
Sinterability and dielectric properties of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 composite ceramics
Qianqian JiaHuiming Ji Xiaolei LiShan Liu Zhengguo Jin 《Journal of Alloys and Compounds》2011,509(41):10155-10160
The composite ceramics of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 (BSCT-CTS-MT) were prepared by the conventional solid-state route. The sintering performance, phase structures, morphologies, and dielectric properties of the composite ceramics were investigated. The BSCT-CTS-MT ceramics were sintered at 1100 °C and possessed dense microstructure. The dielectric constant was tailored from 1196 to 141 as the amount of Mg2TiO4 increased from 0 to 50 wt%. The dielectric constant and dielectric loss of 40 wt% Ba0.55Sr0.4Ca0.05TiO3-10 wt% CaTiSiO5-50 wt% Mg2TiO4 was 141 and 0.0020, respectively, and the tunability was 8.64% under a DC electric field of 8.0 kV/cm. The Curie peaks were broadened and depressed after the addition of CaTiSiO5. The optimistic dielectric properties made it a promising candidate for the application of tunable capacitors and phase shifters. 相似文献
11.
Yuan-Bin Chen 《Journal of Alloys and Compounds》2011,509(37):9226-9229
Solid solutions of (1 − x)La(Co1/2Ti1/2)O3-xLa(Mg1/2Ti1/2)O3 were used to prepare La(Mg1−xCox)1/2Ti1/2O3 using solid-state synthesis. X-ray diffraction patterns of the sintered samples revealed single phase formation. A maximum density of 6.01 g/cm3 was obtained for La(Mg1−xCox)1/2Ti1/2O3 (x = 1) ceramics sintered at 1375 °C for 4 h. The maximum values of the dielectric constant (?r = 29.13) and the quality factor (Q × f = 80,000 GHz) were obtained for La(Mg1−xCox)1/2Ti1/2O3 with 1 wt% ZnO additive sintered at 1375 °C for 4 h. The temperature coefficient of resonant frequency τf was −59 ppm/°C for x = 0.3. 相似文献
12.
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
13.
(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
14.
Microstructure and microwave dielectric properties of Mg-substituted ZnNb2O6-TiO2 microwave ceramics were investigated. Mg acted as a grain refining reagent and columbite phase stabilization reagent. With an increasing Mg content, the amount of ixiolite (Zn, Mg) TiNb2O8 decreased, and the amount of (Zn0.9Mg0.1)0.17Nb0.33Ti0.5O2 and columbite increased. ZnO-Nb2O5-1.75TiO2-5 mol.%MgO exhibited excellent dielectric properties (at 950 °C): ?r = 35.6, Q × f = 16,000 GHz (at 5.6 GHz) and τf = −10 ppm/°C. The material was applied successfully to make RF/microwaves ceramic capacitor, whose self-resonance frequency was 19 GHz at low capacitance of 0.13 pF. 相似文献
15.
Zhihang Peng Qiang ChenJiagang Wu Xiaohong ZhuDingquan Xiao Jianguo Zhu 《Journal of Alloys and Compounds》2011,509(33):8483-8486
Sb5+-doped (NaBi)0.38(LiCe)0.05[]0.14Bi2Nb2O9 (represented as NBNLCS-x, where [] represents A-site vacancies) ceramics were prepared by the conventional solid-state route. The ceramics well sintered to approach ∼98.5% theoretical density and the tetragonality of crystal structure increased with Sb5+ additions. However, the Curie temperature (TC) and the piezoelectric coefficient (d33) of Sb5+-modified ceramics gradually decreased. The 3 mol% Sb5+-doped samples exhibited optimum properties with a d33 value of ∼22 pC/N planar electromechanical coupling factor (kp) of ∼11.2% and relatively high TC of ∼765 °C. These results indicate that NBNLCS-x material is a promising candidate for high-temperature piezoelectric applications. 相似文献
16.
Cheng-Liang Huang Jhih-Yong ChenBing-Jing Li 《Journal of Alloys and Compounds》2011,509(11):4247-4251
The microwave dielectric properties of CaTiO3-added Mg2(Ti0.95Sn0.05)O4 ceramics prepared by the mixed oxide route have been investigated. The combination of spinel-structured Mg2(Ti0.95Sn0.05)O4 and perovskite-structured CaTiO3 forms a two-phase system (1 − x)Mg2(Ti0.95Sn0.05)O4-xCaTiO3, which was confirmed by the XRD patterns and the EDX analysis and it also leads to a zero τf. The microwave dielectric properties of the ceramics can be effectively controlled by varying the x value. For practical applications, a new microwave dielectric material 0.91Mg2(Ti0.95Sn0.05)O4-0.09CaTiO3 is suggested and it possesses a good combination of dielectric properties with an ?r of ∼18.01, a Q × f of ∼92,000 GHz, and a τf of ∼0 ppm/°C, which makes it is a very promising candidate material for high frequency applications. 相似文献
17.
Akira NobutaFeng-Fan Hsieh Tae Ho ShinSou Hosokai Satoshi YamamotoNoriyuki Okinaka Tatsumi IshiharaTomohiro Akiyama 《Journal of Alloys and Compounds》2011,509(33):8387-8391
This study investigated the combined effects of self-propagating high-temperature synthesis (SHS), planetary ball-mill (PBM) treatment, and sintering temperature on La0.7Sr0.3Ga0.7Mg0.1Fe0.2O3−δ (LSGMF73712) as an electrolyte material for solid oxide fuel cells (SOFC). The SHS products (SHS-LSGMF73712) were compared with that prepared via solid-state reaction (SSR) in terms of sinterability and power generation performance. The SHS products were treated with PBM for 10, 30, 50, and 70 h. The SHS products contained the by-product LaSrGaO4; however, in the SHS products treated with PBM for longer than 50 h, the by-product disappeared after sintering at 1350 °C for 3 h in air. Among the samples, SHS products treated with PBM for 70 h displayed superior sintering (1350 °C), whereas the SSR product (SSR-LSGMF73712) was successfully sintered at 1450 °C for 3 h in air. Under the cell configuration of Ni-Fe/SHS-LSGMF73712-PBM70 h (0.3 mm thick)/Sm0.5Sr0.5CoO3, the maximum power density was 0.673 W/cm2 at 800 °C using humidified hydrogen gas (3 mol% H2O) as a fuel and air as an oxidizing agent at a flow rate of 100 mL/min, which was almost equivalent to that using SSR-LSGMF73712 (0.629 W/cm2 at 800 °C) under the same conditions. 相似文献
18.
Hsing-I. Hsiang Li-Then MeiChi-Shiung Hsi Wei-Cheng WuJer-Hao Wu Fu-Su Yen 《Journal of Alloys and Compounds》2011,509(23):6659-6665
The Bi and Zn substitution effects on the sintering behaviors, magnetic and electric properties of hexagonal ferrites with a composition of 2(Ba1−xBixO)·2(ZnyCo0.8−yCu0.2O)·6(Fe2−x/3Znx/3O3) were investigated. The results showed that the addition of Bi and Zn can significantly promote Co2Y densification. The Y phase may be triggered to decompose into M and spinel phases at high sintering temperatures (above 1050 °C) for samples with excess Bi (x = 0.2) substitution, which resulted in densification and magnetic properties degradation. Co2Y ferrites with x = 0.1 and y = 0.4 sintered at 1050 °C show a relative density of 94%, a high initial permeability of 4.5, a quality factor (Q) of 50. 相似文献
19.
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
20.
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