Phase relation and microwave dielectric properties of (Zn _1-xCo_x)Ta₂O₆ system

High-dielectric constant and low-loss ceramics in the (Zn _1-xCo_x)Ta₂O₆ ceramics have been prepared by the conventional mixed oxide route and their microwave dielectric properties have been investigated. A phase change or crossover from ZnTa ₂O₆ to CoTa₂O₆ occurred at x=0.07 and was completed at x=0.11 and it tends to form a continuous solid solution elsewhere. An over-sintered specimen would lead to a slight decrease in the density resulting in a decline of the dielectric constant and the Q × f value. The specimen with x=0.05 possessed an excellent combination of microwave dielectric properties: ε_r∼38.47, Q × f∼112 000 GHz, and τ_f∼11.2 ppm/°C. It is proposed as a candidate material for today's 3G passive components and especially small-sized GPS patch antennas.