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1.
Dong-Wan Kim Kyung Hyun Ko Do-Kyun Kwon Kug Sun Hong 《Journal of the American Ceramic Society》2002,85(5):1169-1172
(1− x )ZnNb2 O6 · x TiO2 ceramics were prepared using both anatase and rutile forms of TiO2 . At a composition of x = 0.58, a mixture region of ixiolite (ZnTiNb2 O8 ) and rutile was observed and the temperature coefficient of resonant frequency (τf ) was ∼0 ppm/°C. We found that although ɛr and τf were comparable, the quality factor ( Q × f , Q ≈ 1/ tan δ, f = resonant frequency) of 0.42ZnNb2 O6 ·0.58TiO2 prepared from anatase and rutile was 6000 and 29 000, respectively. The origin of the difference in Q × f of both samples was investigated by measuring electrical conductivity and by analysis of the anatase–rutile phase transition. The anatase-derived sample had higher conductivity, which was related to the reduction of Ti4+ . It is suggested that the increase of dielectric loss originates from an increase in Ti3+ and oxygen vacancies due to an anatase–rutile phase transition. 相似文献
2.
The BiVO4 additive was found effective for low-temperature firing of ZnNb2 O6 polycrystalline ceramics below 950°C in air without a serious degradation in their microwave dielectric properties. Dense BiVO4 -doped ZnNb2 O6 samples of a relative sintered density over 95% could be prepared even at 925°C. An optimally processed specimen exhibited excellent microwave dielectric properties of Q · f = 55000 GHz, ɛr = 26, and τf =−57 ppm/°C. With increasing BiVO4 addition up to 20 mol% relative to ZnNb2 O6 , while the quality factor Q · f was gradually decreased, the relative dielectric constant, ɛr , was linearly increased and the temperature coefficient of resonant frequency, τf , was slightly increased. The variations in Q · f and ɛr are surely attributable to the residual BiVO4 in the ZnNb2 O6 matrix. An unexpected slight increase in τf is probably due to the formation of the Bi(V,Nb)O4 -type solid solution. 相似文献
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4.
Dong-Wan Kim Do-Kyun Kwon Kug Sun Hong Deug Joong Kim 《Journal of the American Ceramic Society》2003,86(5):795-799
Samples of 1/6Ba5 Nb4 O15 ·5/6BaNb2 O6 along with the pure end members, Ba5 Nb4 O15 and BaNb2 O6 , were sintered under low oxygen partial pressure. The degradation mechanisms of dielectric loss in this reducing atmosphere have been studied. We found that the degradation occurred primarily due to the formation of oxygen vacancies caused by the reduction of Nb5+ . This was determined by measuring the electrical conductivity, and through X-ray photoelectron spectroscopy. More importantly, the dielectric loss of 1/6Ba5 Nb4 O15 ·5/6BaNb2 O6 samples with higher temperature stability was further decreased on sintering in a reducing atmosphere. This observation has been explained by considering the increased porosity and formation of a reduced second phase, Ba0.65 NbO3 . 相似文献
5.
Robert C. Pullar Jonathan D. Breeze Neil McN. Alford 《Journal of the American Ceramic Society》2005,88(9):2466-2471
This paper details the investigation of the quality factor ( Q ), dielectric permittivity (ɛr ) and temperature coefficient of resonant frequency (τf ) of the TE01δ mode of the columbite binary niobate ceramics, with the formula MNb2 O6 where M=2+ cation, in relation to their degree of sintering, microstructure and phase composition. The ceramics were made from a mixed oxide preparative route and fired over a range of temperatures from 800° to 1400°C, and most formed the columbite structure. A comprehensive study was made of the niobates containing the transition metal cations M=Mn2+ , Co2+ , Ni2+ , Cu2+ , and Zn2+ , and the group II metal cations M=Mg2+ , Ca2+ , Sr2+ , and Ba2+ . All columbite niobates were found to have ɛr between 17 and 22 and negative τf values between –45 and –76 ppm/°C, and ZnNb2 O6 , MgNb2 O6 , CaNb2 O6 , and CoNb2 O6 had high Q f values of 84 500, 79 600, 49 600, and 41 700 GHz, respectively. The Q f of MgNb2 O6 was found to rise to over 95 000 GHz when heated at 1300°C for 50 h. 相似文献
6.
M. Granahan M. Holmes W. A. Schulze R. E. Newnham 《Journal of the American Ceramic Society》1981,64(4):68-c-
Grain-oriented ceramics of ferroelectric lead metaniobate have been prepared by molten salt synthesis of anisotropic crystallites followed by doctor blade casting. The sintered ceramics have an orthorhombic texture with elongated c axis grains parallel to the casting direction. This allows efficient poling in directions perpendicular to the tape. 相似文献
7.
Qun Zeng Wei Li Jian-lin Shi Jing-kun Guo 《Journal of the American Ceramic Society》2006,89(10):3305-3307
The effects of V2 O5 addition on the sintering behavior, microstructure, and the microwave dielectric properties of 5Li2 O–0.583Nb2 O5 –3.248TiO2 (LNT) ceramics have been investigated. With addition of low-level doping of V2 O5 (≤2 wt%), the sintering temperature of the LNT ceramics could be lowered down to around 920°C due to the liquid phase effect. A secondary phase was observed at the level of 2 wt% V2 O5 addition. The addition of V2 O5 does not induce much degradation in the microwave dielectric properties but lowers the τf value to near zero. Typically, the excellent microwave dielectric properties of ɛr =21.5, Q × f =32 938 GHz, and τf =6.1 ppm/°C could be obtained for the 1 wt% V2 O5 -doped sample sintered at 920°C, which is promising for application of the multilayer microwave devices using Ag as an internal electrode. 相似文献
8.
Lamrath Abdul Khalam Sherin Thomas Mailadil T. Sebastian 《International Journal of Applied Ceramic Technology》2007,4(4):359-366
The columbites MgNb2 O6 , MgTa2 O6 , and corundum-type Mg4 Nb2 O9 ceramics were prepared by the conventional solid-state ceramic route. The structure and microstructure of the sintered samples were investigated by X-ray diffraction and scanning electron microscopic techniques. The microwave dielectric properties of the samples were measured by the resonance method in the frequency range 4–6 GHz. The dielectric properties have been tailored by forming a solid solution between MgNb2 O6 and MgTa2 O6 and by the substitution of TiO2 for Nb2 O5 in both MgNb2 O6 and Mg4 Nb2 O9 ceramics. The Mg(Nb0.7 Ta1.3 )O6 has ɛr =29, Q u × f =67 800 GHz, and τf =0.8 ppm/°C and the MgO–(0.4)Nb2 O5 –(1.5)TiO2 composition has ɛr =34.5, Q u × f =81 300 GHz, and τf =−2 ppm/°C. 相似文献
9.
Hyo Tae Kim Myoung-Hwa Nam Jong-Hee Kim Sahn Nahm 《International Journal of Applied Ceramic Technology》2009,6(5):587-592
Dolomite-type borate ceramics consisting of CaZrB2 O6 were synthesized via a conventional solid-state reaction route; low-temperature sintering was explored using Bi2 O3 –CuO additives of 1–7 wt% for low-temperature co-fired ceramics applications. For several sintering temperatures, the microwave dielectric properties and chemical resistance of the ceramics were investigated. The CaZrB2 O6 ceramics with 3 wt% Bi2 O3 –CuO addition could be sintered below 925°C, and the microwave dielectric properties of the low-temperature samples were ɛr =10.55, Q × f =87,350 GHz, and τf =+2 ppm/°C. The chemical resistance test result showed that both CaZrB2 O6 - and Bi2 O3 –CuO-added CaZrB2 O6 ceramics were durable in basic solution but were degraded in acid solution. 相似文献
10.
Donhang Liu Yi Liu Shui-Q. Huang Xi Yao 《Journal of the American Ceramic Society》1993,76(8):2129-2132
Phase structures and dielectric properties of the compounds with formulas BixZn2/3 Nb4/3 O4+3x/2 (group M), Bix Zn8/3-x Nb4/3 O6+x/2 (group V), and Bix Zn2-2x/3 Nb2-x/3 O7 (group W) have been investigated. Initial results indicate that a cubic pyrochlore structure is the predominant phase of these compound. Most of the measured ceramic specimens exhibit dielectric properties suitable as temperatures-stable and temperature-compensating dielectrics in the capacitor industry. The values of the dielectric constant K are 80-160, while those of the temperature coefficient are–500 to + 160 ppm/°C. The composition limits of the single pyrochlore phase are determined mainly by Bi2 O3 additives. 相似文献
11.
Chang Wei Zheng Shu Ya Wu Xiang Ming Chen Kai Xin Song 《Journal of the American Ceramic Society》2007,90(5):1483-1486
MgAl2 O4 microwave dielectric ceramics were modified by Zn substitution for Mg, and their dielectric characteristics were evaluated, along with their structures. Dense (Mg1− x Zn x )Al2 O4 ceramics were obtained by sintering at 1550°–1650°C in air for 3 h, and the (Mg1− x Zn x )Al2 O4 solid solution was determined in the entire composition range. With Zn substitution for Mg, the dielectric constant ɛ of MgAl2 O4 just varied from 7.90 to 8.56, while the Q × f value had significantly improved up to a maximal value of 106 000 GHz at x =1.0. Moreover, the τf of MgAl2 O4 ceramics had declined from −73 to −63 ppm/°C. 相似文献
12.
Cubic-pyrochlore-structure α-phase and low-symmetry-structure ß-phase are the basic phases of dielectric ceramics that are based on Bi2 O3 -ZnO-Nb2 O5 (BZN). In this paper, the melting behaviors of the α-phase and the ß-phase have been explored using differential thermal analysis and X-ray diffractometry. The results show that BZN-based α-phase is a congruent compound; its congruent melting point is 1190°C. BZN-based ß-phase is an incongruent compound that dissociates to form α-phase and a liquid phase, with an absorption of heat, at its incongruent melting point (peritectic temperature) of 1100°C. Upon cooling, the α-phase reacts with the liquid phase to form the ß-phase via peritectic reaction. Upon quenching, the BZN-based cubic-fluorite phase precipitates from the liquid phase. 相似文献
13.
Qun Zeng Wei Li Jian-lin Shi Xian-lin Dong Jing-kun Guo 《Journal of the American Ceramic Society》2007,90(7):2262-2265
The effects of the addition of V2 O5 on the sintering behavior, microstructure, and microwave dielectric properties of 5Li2 O–1Nb2 O5 –5TiO2 (LNT) ceramics have been investigated. With low-level doping of V2 O5 (≤3 wt%), the microstructure of the LNT ceramic changed from a special two-level intergrowth structure into a two-phase composite structure with separate grains. And the sintering temperature of the LNT ceramics could be lowered to around 900°C by adding a small amount of V2 O5 without much degradation in microwave dielectric properties. Typically, better microwave dielectric properties of ɛr =41.7, Q × f =7820 GHz, and τ f =45 ppm/°C could be obtained for the 1 wt% V2 O5 -doped ceramics sintered at 900°C. 相似文献
14.
A. de BRETTEVILLE JR. F. A. HALDEN T. VASILOS L. REED 《Journal of the American Ceramic Society》1957,40(3):86-89
Results of studies on the effect of compositional changes and impurities on the electrical characteristics of single-crystal, hot-pressed, and dry-pressed and fired cadmium niobate are presented. Specimens of compositions from CdNb2 O6 to Cd2.1 Nb2 O7.1 were studied optically, electrically, and by X-ray diffraction. Cadmium metaniobate remains paraelectric from –180° to +400°C. and acts primarily as a diluent to the ferroelectric properties of cadmium niobate. The Curie point of cadmium niobate occurs at approximately –85°C. with a dielectric constant peak of 6600 for a [110] crystal cut. Indications of antiferroelectricity are discussed. Room-temperature measurements in the paraelectric phase at 21 kilomegacycles indicate a dielectric constant of 150 with a dissipation factor of less than 0.002 as compared with the high losses of BaTiO3 in this frequency range. 相似文献
15.
W. R. Xue Walter A. Schulze † Robert E. Newnham 《Journal of the American Ceramic Society》1990,73(6):1783-1784
The electromechanical properties of PbTiO3 ceramics, modified by substitution of Sm or Gd + Nd (same average atomic radius as Sm) for Pb, were studied in the range of 6% to 14% substitution. The modified PbTiO3 ceramics were stable, and the Curie temperature decreased linearly over this composition range. The 10% Sm composition had a large anisotropy in the coupling factor ratio, k t / k p , and a similar, but weaker, effect developed for 12% (1/2 Gd + 1/2 Nd). This indicates that other than average ion size may influence the electromechanical coupling factor ratio. 相似文献
16.
Shingo Ishida Feng Ren Nobuyuki Takeuchi 《Journal of the American Ceramic Society》1993,76(10):2644-2648
A new yellow pigment with the pyrochlore structure Cax Y2− x V x Ti2− x O7 was prepared as a substitute for the decreasing variety of available yellow ceramic pigments due to the severe regulation of toxic lead and cadmium. The solubility limit of vanadium in this pigment was found to be 1.5 wt% as V2 O5 or 0.13 as x in the above formula expression. Characterization of vanadium in the vanadium pyrochlore yellow pigment by electron spectroscopy for chemical analysis and electron spin resonance showed that the oxidation state of vanadium was V5+ and its yellow color mostly originated from V5+ substituted for Ti4+ . Comparison of color characteristics of Cax Y2− x V x Ti2− x O7 with those of commercial V–SnO2 and V–ZrO2 revealed that Ca x Y2− x V x Ti2− O7 had better color strength and brightness than the commercial pigments. 相似文献
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18.
Qun Zeng Wei Li Jian-lin Shi Xian-lin Dong Jing-kun Guo 《Journal of the American Ceramic Society》2008,91(2):644-647
A group of new y M-phase/(1− y ) Li2+ x Ti1−4 x Nb3 x O3 composite ceramics with adjustable permittivities for low-temperature co-fired ceramic applications was initially investigated in the study. The 0.5 M-phase/0.5 Li2+ x Ti1−4 x Nb3 x O3 ( x =0.01, 0.02, 0.04, 0.06, 0.081) composite ceramics were first investigated to find the appropriate "Li2 TiO3 ss" composition ( x value). The best dielectric properties of ɛr =40.1, Q × f values up to 9318 GHz, τf =25 ppm/°C, were obtained for the ceramics composites at x =0.02. Based on the good dielectric properties, the suitable "Li2 TiO3 ss" composition with x =0.02 was mixed with the Li1.0 Nb0.6 Ti0.5 O3 powder as the ratio of y "M-phase"/(1− y ) "Li2 TiO3 ss" ( y =0.2, 0.4, 0.5, 0.6, 0.8). By adjusting the y values, the group of composite ceramics could exhibit largely are adjustable permittivities varying from ∼20 to ∼60, while Q × f and τf values relatively good. Nevertheless, in this study, because there are interactions between the M-phase and Li2 TiO3 ss during sintering process, their microwave dielectric properties could not be predicted precisely by the empirical model. 相似文献
19.
Phase stability, sinterability, and microwave dielectric properties of Bi2 W2 O9 ceramics and their cofireability with Ag, Cu, and Au electrodes have been investigated. Single-phase Bi2 W2 O9 powder was synthesized by solid-state reaction in air at 800°C for 3 days. X-ray powder diffraction data show Bi2 W2 O9 to have an orthorhombic crystal structure described by the noncentrosymmetric space group Pna 21 , with lattice parameters a =5.4401(8), b =5.4191(8), c =23.713(4) Å. Ceramics fired at temperatures up to 865°C remain single-phase but above this temperature ferroelectric Bi2 WO6 appears as a secondary phase. The measured relative permittivity of Bi2 W2 O9 ceramics increases continuously from 28.6 to 40.7 for compacts fired between 860° and 885°C. The bulk relative permittivity of Bi2 W2 O9 corrected for porosity was calculated as 41.3. Bi2 W2 O9 ceramics fired up to 875°C exhibit moderate quality factors, Q × f r , ∼7500–7700 GHz and negative temperature coefficient of resonant frequency, ∼−54 to −63 ppm/°C. Chemical compatibility experiments show Bi2 W2 O9 ceramics to react with both Ag and Cu electrodes, but to form good contacts with Au electrodes. 相似文献
20.
Mukkuttiparambil Ayyappan Sanoj Chalappurath Pattelath Reshmi Manoj Raama Varma 《Journal of the American Ceramic Society》2009,92(11):2648-2653
ZnNb2 O6 (ZN) is a columbite-structured niobate compound showing excellent dielectric properties and comparatively low sintering temperatures (∼1200°C). Hence it is a good candidate for possible low-temperature cofired ceramics (LTCC) applications. In the present investigation, ZnNb2 O6 was synthesized in the form of micrometer-sized powder using a conventional solid-state ceramic synthesis route as well as in the form of nanosized powder by a polymer complex method. The finite size effect of ZN particles on sinterability and microwave dielectric properties of sintered pellets was evaluated. The phase formation was confirmed from the X-ray diffraction (XRD) analysis. The particle size distribution of the nanoparticles was found to be of the order of 18–20 nm by using high-resolution transmission electron microscopy analysis and 30 nm by analyzing the XRD patterns using Debye Scherrer's formula, after correcting for the instrument broadening effects. A ZN–60ZnO–30B2 O3 –10SiO2 (ZBS) composite was made by adding predetermined amounts of glasses. The microstructures of the sintered pellets of ZN and ZN–ZBS composites were examined using scanning electron microscopy and analyzed using image analysis. The nano-ZN–ZBS composites were sintered to 93% of the reported density at 925°C/2 h, with microwave dielectric properties of ɛr =22.5, Q × f ∼12 800 GHz, and τf =−69.6 ppm/°C, emerging as a potential material for possible LTCC applications. 相似文献