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1.
Tai-Kwang Park 《Materials Research Bulletin》2008,43(3):730-734
Ceramic powders of (Ba,Pb)Pb(Mg1/3Ta2/3)O3 were prepared via a B-site precursor route. Crystal symmetries and lattice parameters were determined. Monophasic perovskite was developed after the two-step reaction process, in which the lattice parameters showed linear changes in the entire composition range. Dielectric responses of the ceramics with compositional and frequency changes were investigated. The results were also compared with the (Ba,Pb)(Zn1/3Ta2/3)O3 data. 相似文献
2.
Jung-A Lee 《Materials Research Bulletin》2005,40(10):1839-1846
Pb(Zn1/3Ta2/3)O3 ceramics, compositionally modified by the incorporation of Fe to the octahedral lattice sites, were prepared and characterized in terms of perovskite development, dielectric properties, as well as microstructure evolution. The powders of the B-site precursor compositions were synthesized separately and reacted with PbO to form Pb[(Zn1/3Ta2/3),(Fe1/2Ta1/2)]O3. The perovskite contents increased continuously with the Fe concentration. The maximum dielectric constant values of the ceramics increased tremendously with the fraction of Fe, whereas the dielectric maximum temperatures were rather insensitive to the compositional change. 相似文献
3.
Stoichiometric lead magnesium niobate, Pb(Mg1/3Nb2/3)O3 (PMN), perovskite ceramics produced by reaction-sintering process were investigated. Without calcination, a mixture of PbO, Nb2O5, and Mg(NO3)2 was pressed and sintered directly. Stoichiometric PMN ceramics of 100% perovskite phase were obtained for 1, 2, and 4 h sintering at 1250 and 1270 °C. PMN ceramics with density 8.09 g/cm3 (99.5% of theoretical density 8.13 g/cm3) and Kmax 19,900 under 1 kHz were obtained. 相似文献
4.
Microstructure and microwave dielectric characteristics of (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramics
Wen-Cheng Tzou Yao-Sheng Yang Ho-Hua Chung Chien-Chen Diao 《Materials Research Bulletin》2007,42(11):1897-1904
(1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 (0.1 ≤ x ≤ 0.85) composites are prepared by mixing 1150 °C-calcined BaTi4O9 with 1150 °C-calcined Ba(Zn1/3Ta2/3)O3 powders. The crystal structure, microwave dielectric properties and sinterabilites of the (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramics have been investigated. X-ray diffraction patterns reveal that BaTi4O9, ordered and disordered Ba(Zn1/3Ta2/3)O3 phases exist independently over the whole compositional range. The sintering temperatures of (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramics are about 1240 - 1320 °C and obviously lower than those of Ba(Zn1/3Ta2/3)O3 ceramics. The dielectric constants (?r) and the temperature coefficient of resonant frequency (τf) of (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramics increase with the increase of BaTi4O9 content. Nevertheless, the bulk densities and the quality values (Q × f) of (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramics increase with the increase of Ba(Zn1/3Ta2/3)O3 content. The results are attributed to the higher density and quality value of Ba(Zn1/3Ta2/3)O3 ceramics, the better grain growth, and the densification of sintered specimens added a small BaTi4O9 content. The (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramic with x = 0.1 sintered at 1320 °C exhibits a ?r value of 31.5, a maximum Q × f value of 68500 GHz and a minimum τf value of 4.1 ppm/°C. 相似文献
5.
Chun Huy Wang 《Materials Research Bulletin》2004,39(6):851-858
In this work, the piezoelectric ceramic system of Pb[(Zr1−xTix)0.74(Mg1/3Nb2/3)0.20(Zn1/3Nb2/3)0.06]O3, 0.47≤x≤0.57, with composition close to the morphotropic phase boundary, was studied. From the results of X-ray diffraction and piezoelectric measurement, ceramics near x=0.51 were found at the morphotropic phase boundary (MPB) between the tetragonal and pseudocubic perovskite. The planar coupling factor (kp=0.72) is high at compositions near the MPB, but the mechanical quality factor (Qm=75) is low. The calculation of the diffuseness of phase transition shows that the region of phase coexistence of this system is broader than that of the ternary system. 相似文献
6.
La modified Pb(Mg1/2W1/2)O3 were prepared by solid-state reaction process, and the sintering behavior, microstructure and microwave dielectric properties were investigated by X-ray powder diffraction (XRD), Raman scattering and HP network analyzer in this paper. A series of single phase perovskite type solid solutions with A-site vacancies (Pb1−3x/2Lax(Mg1/2W1/2)O3 (0 ≤ x ≤ 2/3)) were formed. The solid solution took cubic perovskite type structure (Fm3m) with random distribution of A-site vacancies when 0 < x < 0.5, and tetragonal or orthorhombic structure with the ordering of A-site vacancies when 0.5 ≤ x ≤ 2/3. The dielectric constant and temperature coefficient of resonant frequency decrease with increasing La content. Relatively good combination microwave dielectric properties were obtained for x = 0.56: ?r = 28.7; Q × f = 18098; and τf = −5.8 ppm/°C. 相似文献
7.
10 mol% Pb(Fe1/2Nb1/2)O3 (PFN) modified Pb(Mg1/3Nb2/3)O3-PbZr0.52Ti0.48O3 (PMN-PZT) relaxor ferroelectric ceramics with compositions of (0.9 − x)PMN-0.1PFN-xPZT (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9) were prepared. X-ray diffraction investigations indicated that as-prepared ceramics were of pure perovskite phase and the sample with composition of x = 0.8 was close to morphotropic phase boundary (MPB) between rhombohedral and tetragonal phase. Dielectric properties of the as-prepared ceramics were measured, and the Curie temperature (Tc) increased sharply with increasing PZT content and could be higher than 300 °C around morphotropic phase boundary (MPB) area. At 1 kHz, the sample with composition of x = 0.1 had the largest room temperature dielectric constant ?r = 3519 and maximum dielectric constant ?m = 20,475 at Tm, while the sample with composition of x = 0.3 possessed the maximum dielectric relaxor factor of γ = 1.94. The largest d33 = 318 pC/N could be obtained from as-prepared ceramics at x = 0.9. The maximum remnant polarization (Pr = 28.3 μC/cm2) was obtained from as-prepared ceramics at x = 0.4. 相似文献
8.
The microwave dielectric properties and the microstructures of Nd(Co1/2Ti1/2)O3 ceramics prepared by conventional solid-state route have been studied. The prepared Nd(Co1/2Ti1/2)O3 exhibited a mixture of Co and Ti showing 1:1 order in the B-site. It is found that low-level doping of B2O3 (up to 0.75 wt.%) can significantly improve the density and dielectric properties of Nd(Co1/2Ti1/2)O3 ceramics. Nd(Co1/2Ti1/2)O3 ceramics with additives could be sintered to a theoretical density higher than 98.5% at 1320 °C. Second phases were not observed at the level of 0.25-0.75 wt.% B2O3 addition. The temperature coefficient of resonant frequency (τf) was not significantly affected, while the dielectric constants (?r) and the unloaded quality factors Q were effectively promoted by B2O3 addition. At 1320 °C/4 h, Nd(Co1/2Ti1/2)O3 ceramics with 0.75 wt.% B2O3 addition possesses a dielectric constant (?r) of 27.2, a Q × f value of 153,000 GHz (at 9 GHz) and a temperature coefficient of resonant frequency (τf) of 0 ppm/°C. The B2O3-doped Nd(Co1/2Ti1/2)O3 ceramics can find applications in microwave devices requiring low sintering temperature. 相似文献
9.
Relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (65/35) and 10% PbZrO3-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (65/35) ceramics were both prepared by a modified precursor method, which was based on the high-temperature synthesis of an oxide precursor that contained all the B-site cations for the consideration of B-site homogeneity. The dielectric properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 (65/35) ceramic was more of normal ferroelectric behavior, but the high dielectric constant (?m = 34,200 at 1 kHz) and piezoelectric constant (d33 = 709 pC/N) were observed for this composition close to the morphotropic phase boundary. Comparatively, introduction of 10% PbZrO3 into Pb(Mg1/3Nb2/3)O3-PbTiO3 (65/35) ceramics enhanced the diffuse phase transition as well as the rhombohedral to tetragonal phase transition temperature, while it also kept the high dielectric constant (?m = 29,600 at 1 kHz) and piezoelectric constant (d33 = 511 pC/N). 相似文献
10.
The effect of oxide additives on the low-temperature sintering and dielectric properties of microwave dielectrics (Zn,Mg)TiO3 have been investigated. The study showed that a small amount of V2O5 accelerated the densification rate of (Zn,Mg)TiO3 dielectrics as compared with the other oxide additives. In addition to lower sintering temperature of zinc titanate dielectrics, the addition of V2O5 decreased the decomposition temperature of (Zn,Mg)TiO3. Additionally, the increased amount of magnesium raised both the sintering temperature and the decomposition temperature of (Zn,Mg)TiO3. Relative permittivity of (Zn,Mg)TiO3 dielectrics decreased accompanied with increase of Q × f as the amount of magnesium content increased. The temperature coefficient of resonant frequency of (Zn,Mg)TiO3 shifted to more negative values as the amount of magnesium increased. 相似文献
11.
Bismuth containing crystalline solutions of (1 − x)Bi(MgZr)0.5O3-xPbTiO3 (BMZ-PT) and [(BiFeO3)y − (BiMg0.5Zr0.5)1−y]x − [PbTiO3]1−x (BMZ-BF-PT) have been developed using conventional ceramic technology. X-ray diffraction analysis reveals that both the systems possess a perovskite structure, in which tetragonal to rhombohedral phase transformation appears for x = 0.55 in BMZ-PT and y = 0.20 in BMZ-BF-PT systems. SEM photographs reveal a uniform grain size distribution in the solid solution matrix with the presence of ferroelectric domains in few of the compositions. Ferroelectric hysteresis (polarization-electric field, P-E) loops reveal that increase in BiFeO3 in BMZ-PT systems results in a decrease in residual polarization of the system with change and distortion in the shape of the (P-E) loops. 相似文献
12.
The effects of B2O3 addition on the microwave dielectric properties and the microstructures of (1−x)LaAlO3-xSrTiO3 ceramics prepared by conventional solid-state routes have been investigated. Doping with 0.25 wt.% B2O3 can effectively promote the densification and the microwave dielectric properties of (1−x)LaAlO3-xSrTiO3 ceramics. It is found that LaAlO3-SrTiO3 ceramics can be sintered at 1400°C due to the liquid phase effect of a B2O3 addition observed by scanning electronic microscopy (SEM). The dielectric constant as well as the Q×f value decreases with increasing B2O3 content. At 1460°C, 0.46LaAlO3-0.54SrTiO3 ceramics with 0.25 wt.% B2O3 addition possesses a dielectric constant (εr) of 35, a Q×f value of 38,000 (at 7 GHz) and a temperature coefficients of resonant frequency (τf) of −1 ppm/°C. 相似文献
13.
Ni Zhong Xian-Lin Dong Da-zhi Sun Ping-hua Xiang Hui Du 《Materials Research Bulletin》2004,39(2):175-184
Ferroelectrics 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) + x mol% WO3 (x=0.1, 0.5, 1, 2) were prepared by columbite precursor method. Electrical properties of WO3-modified ferroelectrics were investigated. X-ray diffraction (XRD) was used to identify crystal structure, and pyrochlore phase were observed in 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3+2 mol% WO3. Dielectric peak temperature decreased with WO3 doping, indicating that W6+ incorporated into PMN-PT lattice. Lattice constant, pyrochlore phase and grain size contribute to the variation of Kmax. Both piezoelectric constant (d33) and electromechanical coupling factors (kp) were enhanced by doping 0.1 mol% WO3, which results from the introduction of “soft” characteristics into PMN-PT, while further WO3 addition was detrimental. We consider that the two factors, introduction of “soft” characteristics and the formation of pyrochlore phase, appear to act together to cause the variation of piezoelectric properties of 0.67PMN-0.33PT ceramics doping with WO3. 相似文献
14.
Alo Dutta 《Materials Research Bulletin》2011,46(4):518-524
The complex perovskite oxide barium iron tantalate (BFT), BaFe1/2Ta1/2O3, strontium iron tantalate (SFT), SrFe1/2Ta1/2O3 and calcium iron tantalate (CFT), CaFe1/2Ta1/2O3 are synthesized by a solid-state reaction technique. Rietveld refinement of the X-ray diffraction data of the samples shows that BFT and SFT crystallize in cubic structure, with lattice parameter a = 4.06 Å for BFT and 3.959 Å for SFT, whereas CFT crystallizes in orthorhombic structure having lattice parameters a = 5.443 Å, b = 5.542 Å and c = 7.757 Å. Fourier transform infrared spectra show two primary phonon modes of the samples at around 450 cm−1 and 620 cm−1. The compounds show significant frequency dispersion in its dielectric properties. The complex impedance plane plots of the samples show that the relaxation (conduction) mechanism in these materials is purely a bulk effect arising from the semiconductive grains. The relaxation mechanism of the samples is modelled by Cole-Cole equation. The frequency dependent conductivity spectra are found to follow the power law. 相似文献
15.
For the first time, we have grown ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Fe1/2Nb1/2)O3 (PMN-PT-PFN) from the melt by the simple slow cooling process. The chemical composition of the single crystals PMN-PT-PFN (0.59/0.31/0.10) is near the morphotropic phase boundary (MPB). X-ray diffraction (XRD) was used to study phase structure of the as-grown crystals, energy dispersive X-ray spectrometer (EDS) and electron probe micro-analyzer (EPMA) were employed to confirm the chemical composition and element distribution of the as-grown crystals, respectively. The ferroelectric, dielectric and piezoelectric properties of the as-grown PMN-PT-PFN (0.59/0.31/0.10) single crystal oriented along the (0 0 1) axis were measured, which showed that the remnant polarization (Pr), coercive electric fields (Ec), the Curie temperature (Tc) and the piezoelectric coefficient (d33) were 50.2 μC/cm2, 13.9 kV/cm, 158 °C and about 1800 pC/N, respectively. All the results indicated that the PMN-PT-PFN (0.59/0.31/0.10) single crystals are promising for applying to field of high frequency. 相似文献
16.
K.P. Surendran 《Materials Research Bulletin》2007,42(10):1831-1844
Ba(Mg1/3Ta2/3)O3 [BMT] dielectric ceramics are prepared by solid state (one step, two step and molten salt synthesis) and wet chemical methods (precipitation, citrate gel and sol-gel). The formation mechanism of BMT in each synthesis technique is discussed. The formation temperature and particle size of the formed BMT were found to be much lesser (in nanometer range) for solution synthesized powders. It is found that synthesis by sol-gel method resulted in the formation of ultra pure nanopowders of BMT at about 600 °C with average crystallite size of about 18 nm where as in solid state synthesis the formation of BMT was formed at about 1100 °C with average crystallite size of 220 nm. On sintering these powders, densification and grain growth of the chemically derived powders were found to be lower than that of solid state synthesized BMT powder. This has resulted in a slight decrease in density and microwave dielectric properties of the solution synthesized BMT samples. It is found that the microwave dielectric properties improved with increase in the average grain diameter of the sintered BMT ceramics. 相似文献
17.
The microwave dielectric properties and the microstructures of the (1−x)MgTiO3-xCaTiO3 ceramic system were investigated. With partial replacement of Mg by Co, dielectric properties of the (1−x)(Mg0.95Co0.05)TiO3-xCaTiO3 ceramics can be promoted. The microwave dielectric properties are strongly correlated with the sintering temperature. At 1275°C, the 0.95(Mg0.95Co0.05)TiO3-0.05CaTiO3 ceramics possesses excellent microwave dielectric properties: a dielectric constant εr of 20.3, a Q×f value of 107 000 ( at 7 GHz) and a τf value of −22.8 ppm/°C. By appropriately adjusting the x value in the (1−x)(Mg0.95Co0.05)TiO3-xCaTiO3 ceramic system, zero τf value can be achieved. With x=0.07, a dielectric constant εγ of 21.6, a Q×f value of 92 000 (at 7 GHz) and a τf value of −1.8 ppm/°C was obtained for 0.93(Mg0.95Co0.05)TiO3-0.07CaTiO3 ceramics sintered at 1275°C for 4 h. 相似文献
18.
In this study, we tried to lower the sintering temperature of Ba0.6Sr0.4TiO3 (BST) ceramics by several kinds of adding methods of Bi2O3, CuO and CuBi2O4 additives. The effects of different adding methods on the microstructures and the dielectric properties of BST ceramics have been studied. In the all additive systems, the single addition of CuBi2O4 was the most effective way for lowering the sintering temperature of BST. When CuBi2O4 of 0.6 mol% was mixed with starting BST powders and sintered at 1100 °C, the derived ceramics demonstrated dense microstructure with a low dielectric constant (? = 4240), low dielectric loss (tan δ = 0.0058), high tunability (Tun = 38.3%) and high Q value (Q = 251). It was noteworthy that the sintering temperature was significantly lowered by 350 °C compared with no-additive system, and the derived ceramics maintained the excellent microwave dielectric properties corresponding to pure BST. 相似文献
19.
Min-Han KimChang-Soo Woo Sahn Nahm Chang-Hack ChoiHwack-Joo Lee Hyun-Min Park 《Materials Research Bulletin》2002,37(3):605-615
Crystal structure and microwave dielectric properties of (1−x)NdAlO3-xCaTiO3 ceramics have been investigated. Crystal structure of the specimens changed with the composition. Rhombohedral structure was found for the specimens with x≤0.1. When 0.3≤x≤0.7, the specimens had the tetragonal structure and it changed to the orthorhombic structure as x exceeded 0.7. Two types of the second phases were observed in (1−x)NdAlO3-xCaTiO3 ceramics. For the specimens with x≤0.5, Nd4Al2O9 phase was observed and Al-rich phase was found in the specimens with x≥0.7. The dielectric constant (εr) and the temperature coefficient of the resonant frequency (τf) increased with the increase of x. The Q×f value of the specimen increased with x and exhibited the maximum value when x=0.5. The microwave dielectric properties of Q×f=45,000 GHz, εr=45 and τf=−1.5 ppm/°C were obtained for 0.3NdAlO3-0.7CaTiO3 ceramics. 相似文献
20.
The effects of B2O3 addition, as a sintering agent, on the sintering behavior, microstructure and microwave dielectric properties of the 11Li2O-3Nb2O5-12TiO2 (LNT) ceramics have been investigated. With the low-level doping of B2O3 (≤2 wt.%), the sintering temperature of the LNT ceramic could be effectively reduced to 900 °C. The B2O3-doped LNT ceramics are also composed of Li2TiO3ss and “M-phase” phases. No other phase could be observed in the 0.5-2 wt.% B2O3-doped ceramics sintered at 840-920 °C. The addition of B2O3 induced no obvious degradation in the microwave dielectric properties but increased the τf values. Typically, the 0.5 wt.% B2O3-doped ceramics sintered at 900 °C have better microwave dielectric properties of ?r = 49.2, Q × f = 8839 GHz, τf = 57.6 ppm/°C, which suggest that the ceramics could be applied in multilayer microwave devices requiring low sintering temperatures. 相似文献