Dielectric properties and crystal structure of (1 − y)(Mg_0.95Ni_0.05)₄Ta₂O₉–y(Ca_0.8Sr_0.2)TiO₃ ceramics

抄録

The microwave dielectric properties and microstructures of (1 − y)(Mg_0.95Ni_0.05)₄Ta₂O₉–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 (Q×f) 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 990 ppm/°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)₄Ta₂O₉–0.7(Ca_0.8Sr_0.2)TiO₃ has an excellent combination of microwave dielectric properties: ε_r ~ 29.8, Q×f ~ 226,000 GHz (at 9 GHz), and τ_f ~ −2.38 ppm/°C sinter at 1350°C. It is proposed as a candidate material for industrial, scientific and medical band components and Global Position System antennas.