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  • 1
    Electronic Resource
    Electronic Resource
    Microwave Dielectric Properties of Low-Fired ZnNb2O6 Ceramics with BiVO4 Addition (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The BiVO4 additive was found effective for low-temperature firing of ZnNb2O6 polycrystalline ceramics below 950°C in air without a serious degradation in their microwave dielectric properties. Dense BiVO4-doped ZnNb2O6 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 ZnNb2O6, 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 ZnNb2O6 matrix. An unexpected slight increase in τf is probably due to the formation of the Bi(V,Nb)O4-type solid solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00871.x
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave Dielectric Properties of Low-Fired Ba5Nb4O15 (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of B2O3 on the sintering temperature and microwave dielectric properties of Ba5Nb4O15 has been investigated using X-ray powder diffraction, scanning electron microscopy, and a network analyzer. Interactions between Ba5Nb4O15 and B2O3 led to formation of second phases, BaNb2O6 and BaB2O4. The addition of B2O3 to Ba5Nb4O15 resulted in lowering the sintering temperature from 1400° to 925°C. Low-fired Ba5Nb4O15 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 B2O3 additions. More importantly, the formation of BaNb2O6 provided temperature compensation. The microwave dielectric properties of low-fired Ba5Nb4O15 had good dielectric properties: Q×f= 18700 GHz, ɛr= 39, and τf= 0 ppm/°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00525.x
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction of BiNbO4-Based Low-Firing Ceramics with Silver Electrodes (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Several commercial silver electrode pastes have been evaluated for use with BiNbO4-based low-firing ceramics. After electrode application and subsequent cofiring, the electrode pattern on the ceramic was no longer visible. A bismuth-rich second phase was present at the electrode/BiNbO4 interface, and silver was detected in the second phase. Systematic X-ray diffractometry analysis of the mixtures between different silver pastes and doped/undoped BiNbO4 revealed an interaction between the silver and the BiNbO4. This reaction was responsible for the disappearance of the silver electrode patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02737.x
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  • 4
    Electronic Resource
    Electronic Resource
    Origin of Microwave Dielectric Loss in ZnNb2O6-TiO2 (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: (1−x)ZnNb2O6·xTiO2 ceramics were prepared using both anatase and rutile forms of TiO2. At a composition of x= 0.58, a mixture region of ixiolite (ZnTiNb2O8) 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 0.42ZnNb2O6·0.58TiO2 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00240.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Nb2O5/ZnO Addition on Microwave Properties of (Zr0.8Sn0.2)TiO4 Ceramics (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effects of Nb2O5 and ZnO addition on the dielectric properties, especially the quality factor, of (Zr0.8Sn0.2)TiO4 (ZST) ceramics were investigated in terms of the sintered density acquired by the zinc. For ZST ceramics with 2 mol% added ZnO, the relative density of the samples decreased with 〉0.5 mol% addition of Nb2O5. On the other hand, for samples with 6 mol% added ZnO, the relative density remained 〉97%, even when the amount of Nb2O5 was increased to 2.0 mol%. When 〉0.5 mol% Nb2O5 was added, both the quality factor and the dielectric constant exhibited similar trends with sintered density. The ZST ceramics with 6 mol% added ZnO, especially, still manifested a quality factor 〉40 000 and a dielectric constant of 37, even when the amount of Nb2O5 was increased, values that are not explainable by the previously suggested electronic defect model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01050.x
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of Copper(II) Oxide Additions to Zinc Niobate Microwave Ceramics on Sintering Temperature and Dielectric Properties (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of CuO additions on the firing temperature of ZnNb2O6 ceramics was investigated using dilatometry, transmission electron microscopy, and X-ray diffractometry. A 5 wt% CuO addition to ZnNb2O6 ceramics significantly lowered the firing temperature from 1150° to ∼900°C. The presence of a CuO-rich intergranular phase in the specimen was observed and was evidence of the formation of a liquid phase during sintering. The composition of the liquid phase was (ZnCu2)Nb2O8. In particular, the low-fired ZnNb2O6 ceramics had good microwave dielectric characteristics—Q×f= 59 500, ɛr= 22.1, τf=–66 ppm/oC. These properties were correlated with the formation of a second phase, (ZnCu2)Nb2O8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00830.x
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  • 7
    Electronic Resource
    Electronic Resource
    Atmospheric Dependence on Dielectric Loss of 1/6Ba5Nb4O15· 5/6BaNb2O6 Ceramics (2003)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Samples of 1/6Ba5Nb4O15·5/6BaNb2O6 along with the pure end members, Ba5Nb4O15 and BaNb2O6, 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 1/6Ba5Nb4O15·5/6BaNb2O6 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, Ba0.65NbO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03377.x
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  • 8
    Electronic Resource
    Electronic Resource
    Origin of a Shrinkage Anomaly in Anatase (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In our present study, a shrinkage anomaly present during sintering in an anatase powder compact was examined. It was observed that the shrinkage stagnates during sintering. This anomaly has been investigated using dilatometry, X-ray powder diffraction, and scanning electron microscopy. Quantitative phase analysis using X-ray diffraction revealed that the shrinkage anomaly is correlated to the phase transition from anatase to rutile. A calculation based on specific volumes of anatase and rutile showed that the phase transition generated 8.6% additional porosity in the anatase powder compact and this retards the densification as well as the shrinkage in the anatase sample. Microstructural observation of anatase and rutile samples having the same shrinkage confirmed this result.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02536.x
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  • 9
    Electronic Resource
    Electronic Resource
    Low-Temperature Co-Fired NPO-Type Ceramic Composition for High-Frequency Capacitor Applications (2003)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 247 (Aug. 2003), p. 385-388 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/47/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.247.385.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Materials Design with Enhanced Temperature Stability of Resonant Frequency for High Frequency Application (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 124-126 (June 2007), p. 173-176 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: For low temperature cofired ceramic (LTCC) materials to achieve increase functionality, aswell as low loss and moderate dielectric constant, it is essential to achieve the temperature stability ofthe resonant frequency. Facing several empirical approaches toward tuning the temperaturecoefficient of the resonant frequency (τf) through the formation of mixtures or a solid-solutionbetween the two end members with opposite signs of τf, which result in higher dielectric loss, we tooka closer look at the texture engineering that determines the anisotropic dielectric properties in bariumniobate ceramics. We demonstrate the advantage of texture engineering for microwave dielectricproperties including temperature stability by control of crystallographic orientation. Also, themonoclinic rare earth niobates are investigated as novel microwave dielectric materials. Furthermore,the stable τf of the rare earth niobates could be efficiently explained through the ferroelastic domainengineering related to phase transformation
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/23/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.124-126.173.pdf
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