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1.
Kazuaki Endo Kenji Fujimoto Kyohei Murakawa 《Journal of the American Ceramic Society》1987,70(9):215-C
The dielectric properties of the Ba (Co1/3 Nb2/3 )O3 –Ba(Zn1/3 Nb2/3 )O3 system were determined. Ba (Co1/3 Nb2/3 )O3 –Ba(Zn1/3 Nb2/3 )O3 has a complex perovskite structure, a high dielectric constant, a low dielectric loss, and a low temperature coefficient of the resonant frequency. A solid-solution ceramic with 0.7Ba (Co1/3 Nb2/3 )O3 ·0.3 Ba(Zn1/3 Nb2/3 )O3 has a dielectric constant of K=33.5, Q=11000 at 6.5 GHz, and a temperature coefficient of the resonant frequency of τf =0 ppm/°C. The temperature coefficient of resonant frequency can be varied by changing the composition. The Q values of the ceramics can be increased by annealing in a nitrogen atmosphere. These ceramics can be used for resonant elements and stabilized oscillators. 相似文献
2.
Ca(Mg1/3 Nb2/3 )O3 (CMN) and Ba(Zn1/3 Nb2/3 )O3 (BZN) ceramic disks were stacked with three stacking schemes, designated as CMN/BZN, CMN/BZN/CMN, and BZN/CMN/BZN, to yield layered dielectric resonators, and the microwave dielectric characteristics were evaluated with the TE01δ mode. Both experiments and finite element analysis showed that the microwave dielectric characteristics of the layered resonator were determined not only by the volume fraction of BZN but also by the stacking scheme. For each stacking scheme, a good combination of microwave dielectric characteristics with an effective dielectric constant of 34.33–34.52, a Q × f value of 58 800–62 080 GHz, and a near-zero temperature coefficient of resonant frequency could be achieved by adjusting the volume fraction of BZN. The effects of the stacking scheme on the microwave dielectric characteristics of the temperature-stable layered resonator were discussed by combining finite element analysis and dielectric composite models. 相似文献
3.
Hanxing Liu Hongtao Yu Zhongqing Tian Zhenghua Meng Zhaohui Wu Shixi Ouyang 《Journal of the American Ceramic Society》2005,88(2):453-455
The microwave dielectric properties of the (1− x )CaTiO3 – x Ca(Zn1/3 Nb2/3 )O3 ceramic system have been investigated. The ceramic samples sintered at 1300°–1450°C for 4 h in air exhibit orthorhombic pervoskite and form a complete solid solution for different x value. When the x value increased from 0.2 to 0.8, the permittivity ɛr decreased from 115 to 42, the unloaded quality factor Q × f increased from 5030 to 13 030 GHz, and the temperature coefficient τf decreased from 336 to −28 ppm/°C. When x =0.7, the best combination of dielectric properties, a near zero temperature coefficient of resonant frequency of τf ∼−6 ppm/°C, Q × f ∼10 860 GHz and ɛr ∼51 is obtained. 相似文献
4.
X. M. Chen D. Liu R. Z. Hou X. Hu X. Q. Liu 《Journal of the American Ceramic Society》2004,87(12):2208-2212
Ca(Zn1/3 Nb2/3 )O3 microwave dielectric ceramics were prepared using a solid-state reaction process, and their microwave dielectric properties were evaluated as functions of sintering and postdensification annealing conditions. The relationship between microwave dielectric properties and processing was interpreted through the variation of microstructures. The dielectric constant showed slight variation with sintering and annealing conditions, but the Q × f value increased at first and then decreased with increased sintering temperature, and annealing in oxygen indicated significant improvement in Q × f , especially for the specimens sintered at higher temperatures. The good microwave dielectric properties were obtained in the ceramics sintered at 1225°C in air for 3 h and annealed at 1100°C in oxygen for 8 h: ɛ= 34.1, Q × f = 15 890 GHz, τf =−48 ppm/°C. 相似文献
5.
High Q ceramics of Ba3 W2 O9 (BW)-substituted Ba(Zn1/3 Nb2/3 ) O3 (BZN) were prepared with a zero τf through the partial substitution of Zn by Ni and Co. The small concentrations of B-site vacancies introduced by the substitution of BW accelerated the kinetics and stability of the cation ordering and lowered the sintering temperature. Dense, zero τf , ordered solid solutions such as 0.99Ba(Zn0.3 Co0.7 )1/3 Nb2/3 O3 –0.01BW with ɛr =34.4 and Q × f =82 000 at ∼8 GHz could be obtained after sintering at 1380°C for 5 h and annealing at 1300°C for 24 h. Partially ordered ceramics in the Zn/Co and Zn/Ni solid solutions show a large gradient in the ordering throughout the pellets, which produces a resonant frequency dependence of their Q × f value. The ordering gradient is associated with the increased constraints on the growth of the 1:2 ordered structure within the interior of larger and thicker pellets and can be minimized by extended annealing. 相似文献
6.
Synthesis of BaCu(B2 O5 ) Ceramics and their Effect on the Sintering Temperature and Microwave Dielectric Properties of Ba(Zn1/3 Nb2/3 )O3 Ceramics 总被引:1,自引:0,他引:1
Min-Han Kim Jong-Bong Lim Jae-Chul Kim Sahn Nahm Jong-Hoo Paik Jong-Hee Kim Kyeong-Soon Park 《Journal of the American Ceramic Society》2006,89(10):3124-3128
BaCu(B2 O5 ) ceramics were synthesized and their microwave dielectric properties were investigated. BaCu(B2 O5 ) phase was formed at 700°C and melted above 850°C. The BaCu(B2 O5 ) ceramic sintered at 810°C had a dielectric constant (ɛr ) of 7.4, a quality factor ( Q × f ) of 50 000 GHz and a temperature coefficient of resonance frequency (τf ) of −32 ppm/°C. As the BaCu(B2 O5 ) ceramic had a low melting temperature and good microwave dielectric properties, it can be used as a low-temperature sintering aid for microwave dielectric materials for low temperature co-fired ceramic application. When BaCu(B2 O5 ) was added to the Ba(Zn1/3 Nb2/3 )O3 (BZN) ceramic, BZN ceramics were well sintered even at 850°C. BaCu(B2 O5 ) existed as a liquid phase during the sintering and assisted the densification of the BZN ceramic. Good microwave dielectric properties of Q × f =16 000 GHz, ɛr =35, and τf =22.1 ppm/°C were obtained for the BZN+6.0 mol% BaCu(B2 O5 ) ceramic sintered at 875°C for 2 h. 相似文献
7.
Single-phase perovskites were formed in the (1−x )Ba(Zn1/3 Nb2/3 )O3 -( x )La(Zn2/3 Nb1/3 )O3 system for compositions with 0.0≤ x ≤0.6. Although the stability of the trigonal "1:2" ordered structure of the Ba(Zn1/3 Nb2/3 )O3 end member is very limited (0.0≤ x ≤0.05), low levels of lanthanum induce a transformation to a cubic, "1:1" ordered structure that has a broad range of homogeneity (0.05≤ x ≤0.6). Samples with x > 0.6 were comprised of La3 NbO7 , ZnO, and a perovskite with x = 0.6. The cubic 1:1 phases were fully ordered and no evidence was found for a compositionally segregated microstructure. These observations could not be reconciled in terms of a "space-charge" model; rather, they supported a charge-balanced, "random-site" structure for the 1:1 cation-ordered Ba(β1/2 'β1/2 ")O3 phases. 相似文献
8.
Ching-Fang Tseng Cheng-Liang Huang Wen-Ruei Yang Cheng-Hsing Hsu 《Journal of the American Ceramic Society》2006,89(4):1465-1470
The microwave dielectric properties and the microstructures of Nd(Zn1/2 Ti1/2 )O3 (NZT) ceramics prepared by the conventional solid-state route have been studied. The prepared NZT exhibited a mixture of Zn and Ti showing 1:1 order in the B-site. The dielectric constant values (ɛr ) saturated at 29.1–31.6. The quality factor ( Q × f ) values of 56 700–170 000 (at 8.5 GHz) can be obtained when the sintering temperatures are in the range of 1300°–1420°C. The temperature coefficient of resonant frequency τf was not sensitive to the sintering temperature. The ɛ r value of 31.6, the Q × f value of 170 000 (at 8.5 GHz), and the τf value of −42 ppm/°C were obtained for NZT ceramics sintering at 1330°C for 4 h. For applications of high selective microwave ceramic resonators, filters, and antennas, NZT is proposed as a suitable material candidate. 相似文献
9.
A narrow region of Zn-vacancy-containing cubic perovskites was formed in the (1− x )Ba3 (ZnNb2 )O9 −( x )Ba3 W2 O9 system up to 2 mol% substitution ( x =0.02). The introduction of cation vacancies enhanced the stability of the 1:2 B-site ordered form of the structure, Ba(Zn1− x □ x )1/3 (Nb1− x W x )2/3 O3 , which underwent an order–disorder transition at 1410°C, ∼35° higher than pure Ba(Zn1/3 Nb2/3 )O3 . The Zn vacancies also accelerated the kinetics of the ordering reaction, and samples with x =0.006 comprised large ordered domains with a high lattice distortion ( c/a =1.226) after a 12 h anneal at 1300°C. The tungstate-containing solid solutions can be sintered to a high density at 1390°C, and the resultant ordered ceramics exhibit some of the highest microwave dielectric Q factors ( Q × f =1 18 000 at 8 GHz) reported for a niobate-based perovskite. 相似文献
10.
Hyun-Jai Kim Sergey Kucheiko Seok-Jin Yoon Hyung-Jin Jung 《Journal of the American Ceramic Society》1997,80(5):1316-1318
Dielectric properties of the system (1 − x)(La1/2 Na1/2 )TiO3 – x Ca(Fe1/2 Nb1/2 )O3 , where 0.4 # x # 0.6, have been investigated at microwave frequencies. The temperature coefficient of resonant frequency (τf ), nearly 0 ppm/°C, was realized at x = 0.58. These ceramics had perovskite structure and showed relatively low dielectric losses. A new dielectric material applicable to microwave devices having Q · f of 12000–14000 GHz and a dielectric constant (εr ) of 59–60 has been obtained at 1300–1350°C for 5–15 h sintering. 相似文献
11.
The Ca(B'1/2 Nb1/2 )O3 [B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] complex perovskites have been prepared by conventional solid-state ceramic route. The structure and microstructure of the ceramics have been characterized by X-ray diffraction and scanning electron microscopy methods. The ceramics have dielectric constant (ɛr ) in the range 23–32, normalized Q -factor ( Q u × f ) 11 000–38 000 GHz and temperature coefficient of resonant frequency (τf ) −43–5.2 ppm/°C. The microwave dielectric properties of Ca(B'1/2 Nb1/2 )O3 ceramics are found to depend on the ionic radii of B'-site elements and tolerance factor ( t ). The substitution of Ba2+ and Sr2+ for Ca2+ resulted a phase transition in Ca(B'1/2 Nb1/2 )O3 ceramics. The (Ca0.05 Ba0.95 ) (Y1/2 Nb1/2 )O3 has τf close to zero (1.2 ppm/°C) with ɛr =35 and Q u × f =48 500 GHz and is proposed as a useful material for base station applications. Dielectric properties of the Ca(B'1/2 Nb1/2 )O3 ceramics were tailored by the addition of TiO2 and CaTiO3 . 相似文献
12.
Lamrat Abdul Khalam Prabhakaran Sreekumari Anjana Mailadil Thomas Sebastian 《International Journal of Applied Ceramic Technology》2009,6(5):571-580
Low-loss dielectric ceramics based on Ba(B'1/2 Ta1/2 )O3 (B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) complex perovskites have been prepared by the solid-state ceramic route. The dielectric properties (ɛr , Q u , and τf ) of the ceramics have been measured in the frequency range 4–6 GHz by the resonance method. The resonators have a relatively high dielectric constant and high quality factor. Most of the compounds have a low coefficient of temperature variation of the resonant frequencies. The microwave dielectric properties have been improved by the addition of dopants and by solid solution formation. The solid solution Ba[(Y1− x Pr x )1/2 Ta1/2 ]O3 has x =0.15, with ɛr =33.2, Q u × f =51,500 GHz, and τf ≈0. The microwave dielectric properties of Ba(B'1/2 Ta1/2 )O3 ceramics are found to depend on the tolerance factor ( t ), ionic radius, and ionization energy. 相似文献
13.
Sergey Kucheiko Dong-Hun Yeo Ji-Won Choi Seok-Jin Yoon Hyun-Jai Kim 《Journal of the American Ceramic Society》2002,85(5):1327-1329
The microwave dielectric properties of CaTi1− x (Al1/2 Nb1/2 ) x O3 solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO3 . The substitution of Ti4+ by Al3+ /Nb5+ improved the quality factor Q of the sintered specimens. A small addition of Li3 NbO4 (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛr ) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τf ) of −2 ppm/K. Li3 NbO4 as a sintering additive had no harmful influence on τf of ceramics. 相似文献
14.
Cheng-Liang Huang Ching-Fang Tseng Wen-Ruei Yang Tung-Jung Yang 《Journal of the American Ceramic Society》2008,91(7):2201-2204
High-dielectric-constant and low-loss ceramics in the (1− x )Nd(Zn1/2 Ti1/2 )O3 – x SrTiO3 system have been prepared by the conventional mixed-oxide route and their microwave dielectric properties have been investigated. A two-phase system was confirmed by the X-ray diffraction patterns, the energy-dispersive X-ray spectrometer analysis, and the measured lattice parameters. Addition of SrTiO3 , having a much smaller grain size in comparison with that of Nd(Zn1/2 Ti1/2 )O3 , could effectively hold back abnormal grain growth in the Nd(Zn1/2 Ti1/2 )O3 matrix. Evaporation of Zn at high temperatures caused an increase in the dielectric loss of the system. The temperature coefficient of resonant frequency increases with increasing SrTiO3 content and tunes through zero at x =0.52. Specimens with x =0.52 possessed an excellent combination of microwave dielectric properties: ɛr ∼54.2, Q × f ∼84 000 GHz, and τf ∼0 ppm/°C. It is proposed as a suitable candidate material for today's 3G passive components and small-sized GPS patch antennas. 相似文献
15.
The effects of calcium substitution on the structural and microwave dielectric characteristics of [(Pb1− x Ca x )1/2 La1/2 ](Mg1/2 Nb1/2 )O3 ceramics (with x = 0.01–0.5) were investigated. All the materials were observed to have an ordered A(B1/2 ' B1/2 " )O3 -type perovskite structure; however, the space group of the structure changed from Fm 3 m to Pa 3 as the calcium content increased to x = 0.1, and then from Pa 3 to R 3¯ at the x = 0.5 composition. During the structural evolution, the lattice parameter of the perovskite cell decreased linearly, and the dielectric constant ( k ) also decreased, from k = 80 to k = 38. However, the product of the quality factor and the resonant frequency ( Q × f ) increased from 50 000 GHz to 90 000 GHz as the calcium content increased. Also, the temperature coefficient of resonant frequency (τƒ ) gradually changed from 120 ppm/°C to −40 ppm/°C as the calcium content increased. At the x = 0.3 composition, a combination of properties— k ∼ 50, Q × f ∼ 86 000 GHz, and τƒ ∼ 0 ppm/°C—can be obtained. 相似文献
16.
Jian Jiang Bian Yun Fei Dong Guo Xiang Song 《Journal of the American Ceramic Society》2008,91(4):1182-1187
The sintering behavior, ordering state, and microwave dielectric properties of Ba1− x La2 x /3 (Zn0.3 Co0.7 )1/3 Nb2/3 O3 Ceramics (0≤ x ≤0.06) were investigated in this paper. The X-ray diffraction (XRD) results show that all samples exhibit a single perovskite phase except for the sample with x ≥0.03. The sinterability is slightly improved by La doping. The long range order (LRO) degree on B-site is greatly increased with the increase of x value up to x =0.015 and then slightly decreased with the further increase of x due to the increasing amount of second phases. The dielectric constant at microwave frequency decreases slightly with the increase of x when x <0.015 and increases slightly with further increasing x for the samples sintered at 1375°C/10 h. The Q × f value increases with x up to x =0.015 and then decreases with further increase of x , which is consistent with the variation trend of LRO degree. The τf value decreases slightly with the increase of x up to 0.006, then increases greatly with the further increase of x . An optimized dielectric properties of ɛ r =34, Q × f =63 159, GHz and τf =5.21 ppm/°C were obtained for the x =0.01 sample sintered at 1425°C/10 h. 相似文献
17.
Keisuke Kageyama 《Journal of the American Ceramic Society》1992,75(7):1767-1771
The microwave dielectric properties and crystal structure of Ba(Zn1/3 Ta2/3 )O3 – (Sr,Ba)(Ga1/2 Ta1/2 )O3 ceramics were investigated in the present study. The Q value of Ba(Zn1/3 Ta2/3 )O3 was improved by adding 5 mol% Sr(Ga1/2 Ta1/2 )O3 . The maximum Q value of Q × f = 162000 GHz was obtained at 0.95Ba(Zn1/3 Ta2/3 )O3 . 0.05Sr(Ga1/2 Ta1/2 )O3 . For this composition, a lattice super structure caused by hexagonal ordering was observed. A further improvement in the Q value was attained when some Sr was replaced with Ba, and 0.95Ba(Zn1/3 Ta2/3 )O3 · 0.05(Sr0.25 Ba0.75 )(Ga1/2 Ta1/2 )O3 exhibited a maximum Q value such that Q × f = 210000 GHz. Despite the increased Q value with the replacement of Sr by Ba, the c/a value, which indicates the degree of lattice distortion, remained constant near 3/2. The Q value thus improved without lattice distortion in the system Ba(Zn1/3 Ta2/3 )O3 -(Sr,Ba)(Ga1/2 Ta1/2 )O3 , whereas the improvement of Q value increased with lattice distortion in the solid solution system with Ba(Zn1/3 Ta2/3 )O3 as an end member. 相似文献
18.
Radhika M. V. Rao Arvind Halliyal † Arun M. Umarji 《Journal of the American Ceramic Society》1996,79(1):257-260
Phase formation and dielectric properties of the compositions in the system [Pb(Fe1/2 Nb1/2 )O3 ]1 _ x –[Pb(Zn1/3 Nb2/3 )O3 ] x were investigated as possible materials for multilayer ceramic capacitors. The formation of the phase with perovskite structure and dielectric properties of ceramics at room temperature in the entire composition range are presented. The undesirable pyrochlore phase can be suppressed up to x = 0.6 by adopting calcination of B-site oxides, followed by reaction with PbO. Compositions in the single-phase range can be sintered at less than 1000°C. 相似文献
19.
We report the microwave dielectric properties and the microstructures of Nd(Co1/2 Ti1/2 )O3 ceramics prepared by the conventional solid-state route. The prepared Nd(Co1/2 Ti1/2 )O3 exhibits a mixture of Co and Ti showing a 1:1 order in the B site. Lowering the sintering temperature (as low as 1260°C) and promoting the densification of Nd(Co1/2 Ti1/2 )O3 ceramics could be effectively achieved by adding CuO (up to 0.75 wt%). At 1350°C, Nd(Co1/2 Ti1/2 )O3 ceramics with 0.5 wt% CuO addition possess a dielectric constant (ɛr ) of 27.6, a Q × f value of 165 000 GHz (at 9 GHz), and a temperature coefficient of resonant frequency (τf ) of −20 ppm/°C. By comparing with pure Nd(Co1/2 Ti1/2 )O3 ceramics, incorporating additional CuO helps to render a dielectric material with a higher dielectric constant, a smaller τf value, and a 20% dielectric loss reduction, which makes it a very promising candidate for applications requiring low microwave dielectric loss. 相似文献
20.
Dong-Wan Kim Jeong-Ryeol Kim Sung-Hun Yoon Kug Sun Hong Chang Kyung Kim 《Journal of the American Ceramic Society》2002,85(11):2759-2762
The effect of B2 O3 on the sintering temperature and microwave dielectric properties of Ba5 Nb4 O15 has been investigated using X-ray powder diffraction, scanning electron microscopy, and a network analyzer. Interactions between Ba5 Nb4 O15 and B2 O3 led to formation of second phases, BaNb2 O6 and BaB2 O4 . The addition of B2 O3 to Ba5 Nb4 O15 resulted in lowering the sintering temperature from 1400° to 925°C. Low-fired Ba5 Nb4 O15 could be interpreted by measuring changes in the quality factor ( Q × f ), the relative dielectric constant (ɛr ), and the temperature coefficient of resonant frequency (τf ) as a function of B2 O3 additions. More importantly, the formation of BaNb2 O6 provided temperature compensation. The microwave dielectric properties of low-fired Ba5 Nb4 O15 had good dielectric properties: Q × f = 18700 GHz, ɛr = 39, and τf = 0 ppm/°C. 相似文献