a b s t r a c tThe microwave dielectric properties and the microstructures of Mg 0.95 Co 0.05 TiO 3 -Ca 0.6 La 0.8/3 TiO 3 ceramics, prepared by a mixed oxide route, have been investigated. With small amount of V 2 O 5 additions, the sintering temperatures of 0.9Mg 0.95 Co 0.05 TiO 3 -0.1Ca 0.6 La 0.8/3 TiO 3 ceramics can be lowered to 1250 • C. The microwave dielectric properties are found strongly correlated with the sintering temperature as well as the amount of V 2 O 5 additions. The Q × f value of 0.9Mg 0.95 Co 0.05 TiO 3 -0.1Ca 0.6 La 0.8/3 TiO 3 increased with increasing temperature to 1250 • C and decreased thereafter. The decrease in Q × f value was coincident with the abnormal grain growth. A maximum Q × f value of 58,000 (GHz) associated with a dielectric constant (ε r ) of 21.7 and a temperature coefficient ( f ) of −10 ppm/ • C, was achieved for 0.25 wt.% V 2 O 5 -doped samples at 1250 • C. Moreover, a cross-coupled compact hairpin filter with designed center frequency of 2.0 GHz is designed and fabricated using the proposed dielectric ceramic to study its performance. It also showed a substantial reduction in both insertion loss and size in comparison with other dielectrics FR4 and alumina.Crown
Mg0.95Ni0.05TiO3 ceramics were prepared by traditional solid-state route using sintering temperatures between 1300 and 1425 °C and holding time of 2–8 h. The sintered samples were characterized for their phase composition, micro-crystalline structure, unit–cell constant, and dielectric properties. A two-phase combination region was identified over the entire compositional range. The effect of sintering conditions was analyzed for various properties. Both permittivity (εr) and Q factor (Qf) were sensitive to sintering temperatures and holding times, and the optimum performance was found at 1350 °C withholding time of 4 h. The temperature coefficient of resonant frequency (τf) in a range from −45.2 to −52 (ppm/°C) and unit–cell constant were not sensitive to both the sintering temperature and holding time. An optimized Q factor of 192,000 (GHz) related with a permittivity (εr) of 17.35 and a temperature coefficient (τf) of −47 (ppm/°C) was realized for the specimen sintered at 1350 °C withholding time of 4 h. For applications of 5G communication device (filter, antennas, etc.), Mg0.95Ni0.05TiO3 is considered to be a suitable candidate for substrate materials.
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