High-dielectric-constant and low-loss microwave dielectric in the Ca(Mg1/3Ta2/3)O3–(Ca0.8Sr0.2)TiO3 solid solution system

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 ɛr and τf 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 τf value can be achieved. The optimal microwave dielectric properties with a dielectric constant (ɛr) value of 43.37, a Q × f value of 46,000 GHz (where f = 6.8 GHz, is the resonant frequency), and a temperature coefficient of resonant frequency (τf) of −2.7 ppm/°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 3 h. 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.