Dielectric properties and crystal structure of (1-y) (Mg_0.95 Ni_0.05)₄Ta₂O_9-y(Ca_0.8Sr_0.2)TiO₃ ceramics

The microwave dielectric properties and microstructures of (1-y)(Mg_0.95Ni_0.05)₄Ta₂O_9-y (Ca_0.8Sr_0.2)TiO₃ ceramics prepared using a mixed oxide route were investigated. (Mg_0.95Ni_0.05)₄Ta₂O₉ has a dielectric constant (ε_r) of ∼12.23, a high quality factor (Qxf ) of ∼442,092 GHz, and a temperature coefficient of resonant frequency (τ_f) of ∼-55 ppm/°C. To produce a temperature-stable material, Ca_0.8Sr_0.2TiO₃, which has a large positive τ_f value of 990ppm/°C, was added to (Mg_0.95Ni_0.05)₄Ta₂O₉. The temperature coefficient of resonant frequency increased with increasing Ca_0.8Sr_0.2TiO₃ content, going through nearly zero at y = 0.7. The microwave dielectric material 0.3(Mg_0.95Ni_0.05)₄Ta₂O_9-0.7(Ca_0.8Sr_0.2)TiO₃ has an excellent combination of microwave dielectric properties: ε_r ∼29.8, Qxf ∼ 226,000GHz (at 9 GHz), and τ_f ∼-2.38ppm/°C sinter at 1350° C. It is proposed as a candidate material for industrial, scienti fic and medical band components and Global Position System antennas.