The crystal structures, phase compositions and the microwave dielectric properties of the (1-x)Ca(Mg1/3Nb2/3)O3-x(Ca0.8Sr0.2)TiO3 perovskite-based composites prepared by the conventional solid state route have been investigated. The formation of solid solution is confirmed by the XRD patterns. A rapid grain growth is observed at temperatures higher than 1470 °C, which would lead to a decrease in the density and Q × f of the ceramics. The temperature coefficient of resonant frequency increases with increasing (Ca0.8Sr0.2)TiO3 content and tunes through near zero at x = 0.3. Specimen using 0.7Ca(Mg1/3Nb2/3)O3-0.3(Ca0.8Sr0.2)TiO3 possesses an excellent combination of microwave dielectric properties: εr ∼ 43.75, Q × f ∼ 45,200 GHz (where f = 6.3 GHz is the resonant frequency) and τf ∼ -4.2 ppm/°C. It is proposed as a suitable candidate material for small-sized GPS patch antennas.
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