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1.
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
2.
The microstructure and microwave dielectric properties of xLa(Mg1/2Ti1/2)O3–(1 − x)Ca0.6La0.8/3TiO3 ceramics system with ZnO additions (0.5 wt.%) investigated by the conventional solid-state route have been studied. Doping with ZnO (0.5 wt.%) can effectively promote the densification and the dielectric properties of xLa(Mg1/2Ti1/2)O3–(1 − x)Ca0.6La0.8/3TiO3 ceramics. 0.6La(Mg1/2Ti1/2)O3–0.4Ca0.6La0.8/3TiO3 ceramics with 0.5 wt.% ZnO addition possess a dielectric constant (r) of 43.6, a Q × f value of 48,000 (at 8 GHz) and a temperature coefficient of resonant frequency (τf) of −1 ppm/°C sintering at 1475 °C. As the content of La(Mg1/2Ti1/2)O3 increases, the highest Q × f value of 62,900 (GHz) for x = 0.8 is achieved at the sintering temperature 1475 °C. A parallel-coupled line band-pass filter is designed and simulated using the proposed dielectric to study its performance. 相似文献
3.
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
4.
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
5.
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
6.
Mingzhe Hu Chunya LuoHuyong Tian Haoshuang Gu 《Journal of Alloys and Compounds》2011,509(6):2993-2999
The phase evolution, crystal structure and dielectric properties of (1 − x)Nd(Zn0.5Ti0.5)O3 + xBi(Zn0.5Ti0.5)O3 compound ceramics (0 ≤ x ≤ 1.0, abbreviated as (1 − x)NZT-xBZT hereafter) were investigated. A pure perovskite phase was formed in the composition range of 0 ≤ x ≤ 0.05. The B-site Zn2+/Ti4+ 1:1 long range ordering (LRO) structure was detected by both XRD and Raman spectra in x ≤ 0.05 samples. However, this LRO structure became gradually degraded with an increase in x. The dielectric behaviors of the compound ceramic at various frequencies were investigated and correlated to its chemical composition and crystal structure. A gradually compensated τf value was obtained in (1 − x)NZT-xBZT microwave dielectrics at x = 0.03, which was mainly due to the dilution of dielectric constant in terms of Claussius-Mossotti differential equation. 相似文献
7.
(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
8.
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
9.
Keita TaniguchiNoriyuki Okinaka Tomohiro Akiyama 《Journal of Alloys and Compounds》2011,509(10):4084-4088
This paper proposes La1−xKxFeO3 prepared by self-propagating high-temperature synthesis (SHS) as an alternative to platinum catalysts for promoting diesel soot combustion. The catalytic property of eleven products SHSed with different substitution ratios of potassium (x = 0-1) was experimentally evaluated using a thermobalance. In the mass loss curves of the product, T50 was defined as the temperature at which the weight of the reference soot decreases to half its initial weight. The BET specific surface area of SHSed La1−xKxFeO3 depended on x strongly. All the products showed good oxidation catalytic activity. Despite having the smallest surface area (0.11 m2/g) among the obtained products, La0.9K0.1FeO3 (x = 0.1) was found to be the best catalyst with the lowest T50 (442 °C). T50 of La1−xKxFeO3 decreased with increasing x for x > 0.2. The products with x = 0.6 and 0.8 were the second-best catalysts in terms of their T50. Moreover, average apparent activation energy of La0.9K0.1FeO3 (x = 0.1) calculated by Friedman method using TG was as much as 61 kJ/mol lower than that of Pt/Al2O3 catalyst. In conclusion, potassium-substituted SHSed La1−xKxFeO3 can be used as an alternative to Pt/Al2O3 for soot combustion. 相似文献
10.
A series of highly (1 1 1)-oriented tetragonal Nb-doped Pb(Zr0.2Ti0.8)O3 (PNZT) films with and without Pb0.8La0.1Ca0.1Ti0.975O3 (PLCT) seed layer were deposited on the Pt(1 1 1)/Ti/SiO2/Si substrates by sol-gel processing; it was found the pyroelectric properties and fatigue resistance characteristics of PNZT films could be improved by introducing PLCT seed layer. Because the rough surface structures of 5 nm-thick PLCT seed layer can offer nucleation sites to reduce activation energy for the crystallization and lead to the polarization response easily, a large pyroelectric coefficient (460 μC/(m2 K)) and a high figure-of-merit (Fd = 161 μC/(m2 K)) was obtained for PLCT/PNZT/PLCT structure film. It was also found that PLCT seed layer could act as a capacitive interface layer possibly compensating for the vacancy-type defects from PNZT film effectively, which results in enhanced fatigue resistance characteristics of PLCT/PNZT/PLCT structure film. 相似文献
11.
Cheng-Liang Huang Yu-Hua ChienChen-Yi Tai Chi-Yuen Huang 《Journal of Alloys and Compounds》2011,509(9):L150
The microwave dielectric properties and the microstructures of (Mg1−xZnx)Al2O4 (x = 0-0.1) ceramic system prepared by the conventional solid-state route were investigated. The forming of spinel-structured (Mg1−xZnx)Al2O4 (x = 0-0.1) solid solutions was confirmed by the XRD patterns and the measured lattice parameters, which linearly varied from a = b = c = 8.0815 Å for MgAl2O4 to a = b = c= 8.0828 Å for (Mg0.9Zn0.1)Al2O4. By increasing x, the Q × f of (Mg1−xZnx)Al2O4 can be tremendously boosted from 82,000 GHz at x = 0 to a maximum of 156,000 GHz at x = 0.05. The Zn substitution was effective in reducing the dielectric loss without detrimental effects on the ?r and τf values of the ceramics. 相似文献
12.
M.A. Ahmed Samiha T. BishayS.I. El-dek G. Omar 《Journal of Alloys and Compounds》2011,509(30):7891-7894
NixMn0.8−xMg0.2Fe2O4; 0.1 ≤ x ≤ 0.35 was prepared by standard ceramic technique at sintering temperature 1200 °C using heating / cooling rate 4 °C/min. The samples were irradiated by Nd YAG pulsed laser with energy of the pulse 250 mJ. X-ray diffractograms reveal cubic spinel structure for all the samples before and after laser irradiation. After laser irradiation, better crystallinity was obtained in a form of an increase in the calculated crystal size. This increase was discussed as due to the change in the valence of some ions like Fe3+, Ni2+ and Mn2+. The conductivity of all the investigated samples decreases after laser irradiation and becomes temperature independent for a wider range than that before irradiation. This was ascribed to electron rearrangement after laser irradiation. Accordingly, these ferrites are recommended to be useful in electronic devices. 相似文献
13.
Marin Cernea Roxana TruscaRoxana Radu Cristina Valsangiacom 《Journal of Alloys and Compounds》2011,509(41):9934-9937
BaTi0.87Sn0.13O3 (BTS13) nanopowder was prepared by low-temperature aqueous synthesis (LTAS) method. The evolution of the structure and microstructure of the precursor precipitate, heated at temperatures up to 1000 °C was studied by TGA, FT-IR, SEM and XRD techniques. The dried precipitate showed a microstructure consisting of nano-sized grains (∼40 nm) with great tendency to agglomeration. BaTi0.87Sn0.13O3 single phase was obtained at 800 °C. The ceramics prepared from as-obtained BTS13 powders (60-70 nm) show good dielectric and ferroelectric characteristics. The dielectric constant was about 4800 and the dielectric loss (tan δ) was 0.229 at 1 kHz and at the Curie temperature (31 °C). The remanent polarization (Pr) and the coercive field (EC) of Ba0.97Ho0.03TiO3 ceramics, at 1 kHz, were Pr = 13 μC/cm2 and EC = 0.89 kV/cm. The ferroelectric parameters EC and Pr decrease with increasing frequency in the domain 100 Hz to 10 kHz. 相似文献
14.
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
15.
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
16.
The anisotropy compensation and magnetostrictive properties of Tb1−xHox(Fe0.8Co0.2)2 (0.60 ≤ x ≤ 1.0) alloys have been investigated. The easy magnetization direction (EMD) at room temperature rotates from the 〈1 1 1〉 axis (x ≤ 0.75) to the 〈1 0 0〉 axis (x ≥ 0.90) through an intermediate state 〈1 1 0〉, subjected to the anisotropy compensation between Tb3+ and Ho3+ ions. Composition anisotropy compensation is realized near x = 0.75. The Tb0.25Ho0.75(Fe0.8Co0.2)2 alloy has a minimum anisotropy and a large spontaneous magnetostriction coefficient λ111 (≈740 ppm) at room temperature. The strong 〈1 1 1〉-oriented 1-3 epoxy-bonded composite has been fabricated by curing under a moderate magnetic field. A high low-field magnetostriction of about 400 ppm at 3 kOe is obtained for the 1-3 epoxy/Tb0.25Ho0.75(Fe0.8Co0.2)2 composite with 40-vol% alloy particles, which can be attributed to the low magnetic anisotropy, EMD lying along 〈1 1 1〉 direction, the strong 〈1 1 1〉-textured orientation and the chain structure. 相似文献
17.
NixMn0.8−xMg0.2Fe2O4; 0.0≤ x ≤0.40 was prepared by standard ceramic technique, presintering was carried out at 900 °C and final sintering at 1200 °C with heating/cooling rate 4 °C/min. X-ray diffraction analyses assured the formation of the samples in a single phase spinel cubic structure. The calculated crystal size was obtained in the range of 75-130 nm. A slight increase in the theoretical density and decrease in the porosity was obtained with increasing the nickel content. This result was discussed based on the difference in the atomic masses between Ni (58.71) and Mn (54.938). IR spectral analyses show four bands of the spinel ferrite for all the samples. The conductivity and dielectric loss factor give nearly continuous decrease with increasing Ni-content. This was discussed as the result of the significant role of the multivalent cations, such as iron, nickel, manganese, in the conduction mechanism. Anomalous behavior was obtained for the sample with x = 0.20 as highest dielectric constant, highest dielectric loss and highest conductivity. This anomalous behavior was explained due to the existence of two divalent cations on B-sites with the same ratio, namely, Mg2+ and Ni2+. 相似文献
18.
Zhenzhu Cao Guorong Li Jiangtao ZengSiu Wing Or Liaoying ZhengQingrui Yin Lihong Cheng 《Journal of Alloys and Compounds》2011,509(36):8907-8911
The phase transition behavior and its effect on thermal stability of the piezoelectric properties of the (1 − x)[0.65PbMg1/3Nb2/3O3-0.35PbTiO3]-xBiZn1/2Ti1/2O3 ceramics with 0 ≤ x ≤ 0.06 were investigated. The phase transition from the monoclinic to tetragonal phase was determined by the dielectric constant and elastic constant measurements. The temperature independent piezoelectric response with −d31 = 188 pC/N was obtained from 175 to 337 K for the composition with x = 0.02. The enhanced thermal stability of piezoelectric response was achieved by shifting the monoclinic-tetragonal phase transition to the lower temperature. 相似文献
19.
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
20.
Fei ZhouLang Wu Naiming LiuYuancheng Teng Yuxiang LiJianwu Wen Xuetan Ren 《Journal of Alloys and Compounds》2012,512(1):52-56
Lead-free piezoelectric ceramics (0.8 − x)BaTiO3-0.2Bi0.5Na0.5TiO3-xBaZrO3 (BT-BNT-xBZ, 0 ≤ x ≤ 0.08) doped with 0.3 wt% Li2CO3 were prepared by conventional solid-state reaction method. With the Li2CO3 doping, all the ceramics can be well sintered at 1170-1210 °C. The phase structure, dielectric, ferroelectric and piezoelectric properties of the ceramics were investigated. Results show that a morphotropic phase boundary (MPB) between tetragonal and pseudocubic phases exists at x = 0.03-0.04. The addition of Zr can improve the piezoelectric properties of BT-BNT ceramics. Furthermore, a relaxor behavior is induced and the tetragonal-cubic phase transition shifts towards lower temperatures after the addition of Zr. The ceramics with x = 0.03 possess the optimum electrical properties: d33 = 72 pC/N, kp = 15.4%, ?r = 661, Pr = 18.5 μC/cm2, Ec = 34.1 kV/cm, Tc = 150 °C. 相似文献