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Abstract: High-relative-permittivity and low-loss ceramics in the (1− x)Ca(Mg1/3Ta2/3)O3–xCa0.8Sm0.4/3TiO3 system have been prepared by the conventional solid state route and their microwave dielectric properties have been investigated. (1− x)Ca(Mg1/3Ta2/3)O3–xCa0.8Sm0.4/3TiO3 solid solution exhibited orthorhombic crystal structures for all compositions. A rapid grain growth is observed at temperatures higher than 1450°C, which would lead to a decrease in the density and the Q × f of the ceramics. A near-zero temperature coefficient of resonant frequency can be achieved for Ca(Mg1/3Ta2/3)O3 with the addition of Ca0.8Sm0.4/3TiO3. The temperature coefficient of resonant frequency increases with increasing Ca0.8Sm0.4/3TiO3 content and tunes through zero at x =0.45. Specimen using 0.55Ca(Mg1/3Ta2/3)O3–0.45Ca0.8Sm0.4/3TiO3 possesses an excellent combination of microwave dielectric properties: ɛ r ∼44.96, Q × f ∼41,700GHz (where f =6.6GHz, is the resonant frequency) and τ f value of 0ppm/°C. It is proposed as a suitable candidate material for today''s 3G passive components and small-sized GPS patch antennas. [Copyright &y& Elsevier]

Abstract: Low-loss Mg1.8Ti1.1O4 ceramics were prepared by the conventional solid-state route and their microwave dielectric properties were investigated for the first time. The forming of tetragonal-structured Mg1.8Ti1.1O4 main phase associated with a second phase MgTiO3 were confirmed by the X-ray diffraction patterns. However, the presence of the second phase would cause no significant variance in the dielectric properties of the specimen because the second phase properties are very similar to that of the main phase. A fine combination of microwave dielectric properties (ɛ r ∼15.74, Q × f ∼141,000GHz at 10.57GHz, τ f ∼−52.4ppm/°C) was achieved for Mg1.8Ti1.1O4 ceramics sintered at 1450°C for 4h. [Copyright &y& Elsevier]

Abstract: Rock-salt-structured Li2MgTiO4 ceramic was prepared by the conventional mixed oxide route and its microwave dielectric properties were investigated. The microstructures of the ceramics were characterized by SEM. The dielectric properties of the ceramics exhibited a significant dependence on the sintering condition and crystal structure. A new microwave dielectric material, Li2MgTiO4 sintered at 1360°C has a dielectric constant (ɛ r ) of ∼17.25, a Q × f of ∼97,300GHz (where f =9.86GHz, is the resonant frequency) and a τ f of ∼–27.2ppm/°C. The microwave dielectric properties of the ceramic are reported for the first time. [Copyright &y& Elsevier]

Abstract: The crystal structures, phase compositions and the microwave dielectric properties of the (1− x)Ca(Mg1/3Ta2/3)O3–x(Ca0.8Sr0.2)TiO3 perovskite-based composites have been investigated. The (1− x)Ca(Mg1/3Ta2/3)O3–x(Ca0.8Sr0.2)TiO3 solid solutions exhibited an 1:2 ordered monoclinic structure for all compositions. As (Ca0.8Sr0.2)TiO3 content increases, the ɛ r and τ f values increase gradually, while the Q × f values decreases. By appropriately adjusting the x value in the (1− x)Ca(Mg1/3Ta2/3)O3–x(Ca0.8Sr0.2)TiO3 ceramic system, a near-zero τ f value can be achieved. The optimal microwave dielectric properties with a dielectric constant (ɛ r ) value of 43.37, a Q × f value of 46,000GHz (where f =6.8GHz, is the resonant frequency), and a temperature coefficient of resonant frequency (τ f ) of −2.7ppm/°C can be obtained for specimen using (1− x)Ca(Mg1/3Ta2/3)O3–x(Ca0.8Sr0.2)TiO3 (x =0.4) sintered at 1425°C for 3h. It is proposed as a high-dielectric-constant, low-loss dielectric and in particular, a suitable candidate material for today''s 3G passive components and small-sized GPS patch antennas. [Copyright &y& Elsevier]