Improved high Q value of (1 - x)Ca(Mg_1/3Ta_2/3)O₃-xCa_0.8Sm_0.4/3TiO₃ solid solution with zero temperature coefficient of resonant frequency

High-relative-permittivity and low-loss ceramics in the (1 - x)Ca(Mg_1/3Ta_2/3)O₃-xCa_0.8Sm_0.4/3TiO₃ system have been prepared by the conventional solid state route and their microwave dielectric properties have been investigated. (1 - x)Ca(Mg_1/3Ta_2/3)O₃-xCa_0.8Sm_0.4/3TiO₃ 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(Mg_1/3Ta_2/3)O₃ with the addition of Ca_0.8Sm_0.4/3TiO₃. The temperature coefficient of resonant frequency increases with increasing Ca_0.8Sm_0.4/3TiO₃ content and tunes through zero at x = 0.45. Specimen using 0.55Ca(Mg_1/3Ta_2/3)O₃-0.45Ca_0.8Sm_0.4/3TiO₃ possesses an excellent combination of microwave dielectric properties: ε_r ∼ 44.96, Q × f ∼ 41,700 GHz (where f = 6.6 GHz, is the resonant frequency) and τ_f value of 0 ppm/°C. It is proposed as a suitable candidate material for today's 3G passive components and small-sized GPS patch antennas.