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  • 1
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    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 microwave dielectric properties of CaTi1−x(Al1/2Nb1/2)xO3 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 Li3NbO4 (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. Li3NbO4 as a sintering additive had no harmful influence on τf of ceramics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    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 microwave dielectric properties of (1 –x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 (0 ≤x≤ 1.0) ceramics were investigated. (Al1/2Ta1/2)O2 and (Mg1/3Ta2/3)O2 had orthorhombic and tetragonal structure, respectively. As (Mg1/3Ta2/3)O2 concentration increased, (1 – x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 transformed to tetragonal structure. Specimens having a tetragonal single phase could be obtained for x 〉 0.6. As (Mg1/3Ta2/3)O2 concentration increased, the grain size, dielectric constant (ɛr) and quality factor (Q) significantly increased, and the temperature coefficient of resonant frequency (τf) changed from a negative to a positive value. A τf of 0 ppm/°C was realized at x= 0.65 and the Qfo value and ɛr for this composition were 112 470 GHz and 26.1, respectively. The relationship between microstructures and dielectric properties was also investigated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    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 dielectric properties of (Pb1−xCax){(Fe1/2Nb1/2)1–ySny}O3 solid solutions, where 0.4 lessthan equal tox ≤ 0.6, y = 0.05, 0.1, have been investigated at microwave frequencies. The replacement of Fe3+/Nb5+ by Sn4+ at the B–site of the perov-skite structure considerably improves the loss quality factor Q and does not remarkably affect the dielectric constant epsilonr and the temperature coefficient of resonant frequency tauf. The tauf value of nearly 0 ppm/°C can be realized for x= 0.55. New high-quality dielectric ceramics having epsilonr of 85.3-89.9,Qf values of 7510-8600 GHz, and τf of 0-9 ppm/°C were obtained at 1150°C for 3 h sintering in air. The influence of the sintering atmosphere on dielectric properties was also investigated.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The change in dielectric constant of ferroelectric materials as a function of electric field isthe key to wide range of microwave application such as tunable filter, impedance matching network,and phase shifter. In this study, ferroelectric Ba0.5Sr0.5TiO3 (BST) films were grown on r-cut sapphireand polycrystalline sapphire (poly-sapphire) substrates by RF sputtering. The results ofcomprehensive structural diagnostics of the films are correlated with the dielectric constant anddielectric loss of a co-planar BST varactor, measured at a frequency range of 1~3 GHz. Textured BSTfilms approximately 500 nm thick, grown on r-cut sapphire substrates, are characterized by highdielectric constant ≥ 650. However, polycrystalline BST films, grown on poly-sapphire substrates, areless strained, having dielectric constant range of 430 ~ 640
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 45 (Oct. 2006), p. 2332-2336 
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: The microwave dielectric properties of (300-X) nm MgTiO3/(X) nm CaTiO3 thin films have beeninvestigated with correlation between the interface and stress induced by dielectric layers with heattreatment.As the thickness (X) of CaTiO3 film increased, the dielectric constant increased and thetemperature coefficient of the dielectric constant changed from the positive to the negative valuesby the dielectric mixing rule. The dielectric loss of (300-X) nm MgTiO3/(X) nm CaTiO3 thin filmsincreased with an increase of the thickness (X) of CaTiO3 film because of higher thermal stressinduced by the higher thermal expansion coefficient of CaTiO3 than that of MgTiO3
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 45 (Oct. 2006), p. 2351-2354 
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: The dielectric properties of (Ba,Sr)TiO3 (BSTO) and Zr doped BSTO thin films have beeninvestigated to identify candidate thin film dielectric materials having low dielectric loss withoutdegradation of the tunability by continuous composition spread (CCS) technique using off-axis rfmagnetron sputtering. The optimized properties of BSTO thin films deposited on Pt/SiO2/Sisubstrate by CCS were dielectric loss 0.031, tunability 31.5, respectively. The optimized propertiesof Zr doped BSTO thin films deposited on Pt/SiO2/Si substrate by CCS were improved by dielectricloss 42%, FOM 68% at the same BSTO composition, respectively. To confirm the dielectricproperties and compositions by CCS technique, Zr doped BSTO bulk ceramics were evaluated
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 10 (1999), S. 661-666 
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The microwave dielectric properties of (Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 ceramics (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1) and design of 900 MHz band 2-pole monoblock band pass filter (BPF) have been investigated to fabricate BPF. Single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the compositions of Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1). The substitution of Sn for Fe0.5Nb0.5) significantly increased the quality factor Q and slightly decreased the dielectric constant (ɛr). The temperature coefficient of the resonant frequency of 0 ppm °C−1 was realized at x = 0.55 and y = 0.1. The Q · f 0 value and (ɛr) for this composition were found to be 8600 GHz and 86, respectively. A monoblock λ/4 dielectric BPF for 900 MHz band portable telephone terminal is presented. This BPF is a kind of combline filter. Computer-aided design (CAD) was used in the modeling procedure. The equivalent circuit of the monoblock BPF is represented by transmission lines and lumped elements based on Zoe and Zoo. A BPF model was designed for surface mounted device (SMD) types. The simulations of the equivalent circuit and BPF structure have been performed to optimize the filter design. Newly developed Pb0.45Ca0.55){(Fe0.5Nb0.5)0.9Sn0.1}O3 dielectric materials were used for BPF fabrication. Experimental results of the fabricated device were in good agreement with the simulation.
    Type of Medium: Electronic Resource
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