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The effects of Ni substitution for Zn on microwave dielectric properties of (Zn1−x Ni x )3Nb2O8 (x =0.02–0.08) ceramics were investigated in this study. The XRD patterns of the sintered samples reveal single-phase formation with a monoclinic structure. The tremendous improvement of Q × f value can be achieved by a small level of Ni substitution (x =0.05). The τ f value was found to decrease with a decreasing A-site bond valence. In addition, B2O3 and CuO were used as a sintering aid to lower the sintering temperature from 1180 to 900°C. Excellent microwave dielectric properties (ɛ r ∼20.7, Q × f ∼98,000GHz and τ f ∼−85.2ppm/°C) and a chemical compatibility with Ag electrodes can be obtained for 4wt% B2O3–CuO doped (Zn0.95Ni0.05)3Nb2O8 ceramics sintered at 930°C for 2h. This constitutes a very promising material for LTCC applications. [ABSTRACT FROM AUTHOR]

Abstract: The microwave dielectric properties of the (1− x)Li2TiO3–xZnO (x =0.1–0.5) ceramic system prepared by mixed oxide route have been investigated. The rock-salt structured (1− x)Li2TiO3–xZnO were characterized by using X-ray diffraction spectra, scanning electron microcopy (SEM). The dielectric properties are strongly dependent on the compositions, the densifications and the microstructures of the specimens. The decrease of Q × f value at high-level ZnO addition (x >0.3) was owing to the intensity of the (002) superstructure reflection decreased and became disordered rock-salt structure. For practical applications, a new microwave dielectric material 0.7Li2TiO3–0.3ZnO is suggested and it possesses a good combination of dielectric properties with an of ∼22.95, a Q × f of ∼99,800GHz (measured at 8.91GHz), and a of ∼0ppm/°C. A low-loss dielectric resonant antenna using aperture-coupled cylindrical dielectric resonant was designed and fabricated using the proposed dielectric to study its performance. [Copyright &y& Elsevier]

Abstract: (Mg1−x Zn x )1.8Ti1.1O4 (x =0.03–1.00) ceramics were prepared via the conventional solid-state method and their dielectric properties were investigated in the microwave frequency region. Formation of solid solutions was confirmed by the X-ray diffraction analysis, the EDX analysis, and the measured lattice parameters. A small amount of Zn substitution for Mg produced a large increase in Q × f due to a high packing fraction as well as a high relative density of the ceramics. By increasing x from 0.00 to 0.06, the Q × f of the specimen could be tremendously improved from 141,000 to a maximum of 210,700GHz (at 10.52GHz), demonstrating an unique potential for low-loss microwave applications. The τ f values were found to retain in the range from −54.2 to −62.3ppm/°C for all compositions because the resultant change of unit cell volume was small. Also, a remarkable lowering of the sintering temperature down to ∼300°C was observed when Mg was totally substituted by Zn, thereby making it possible for low firing applications. [Copyright &y& Elsevier]

The effects of sintering aids addition on the microstructures and microwave dielectric properties of NdAlO3 ceramics were investigated. V2O5 was selected as liquid phase sintering aid to lower the sintering temperature of NdAlO3 ceramics. With V2O5 addition, the densification temperature of NdAlO3 can be effectively reduced from 1650 °C to 1390∼1410 °C. The crystalline phase exhibited no phase differences at low addition level while Nd4Al2O9 and NdAl11O18 present as second phases as the addition level was over 1 wt.%. The quality factor Q×f was strongly dependent upon the amount of additions. Q×f values of 64,000 GHz and 48,000 GHz could be obtained at 1390∼1410 °C with 0.25 wt.% and 0.5 wt.% V2O5 addition, respectively. During all addition ranges, the relative dielectric constants were not significantly different and ranged from 21.6 to 22.5.The temperature coefficients varies from –31∼–43 ppm/°C. [ABSTRACT FROM AUTHOR]