Synthesis and Microwave Dielectric Properties of Cu‐Doped ZnAl 2 O 4

Spinel materials of composition Zn 1− x Cu x Al 2 O 4 (ZCA, x = 0–0.015) were prepared via the conventional solid‐state route. The lattice structure, microstructure, and microwave dielectric properties were investigated as a function of Cu content. Cu doping was found to improve the sinterability and, meanwhile, significantly increase the quality factor ( Q × f 0 ), which is due to the Cu‐O bond is stronger than Zn‐O bond, and inhibit the oxygen vacancy considered to be responsible for the enhanced Q × f 0 value of ZCA materials. The best microwave dielectric properties were obtained in Zn 0.99 Cu 0.01 Al 2 O 4 with ε r = 8.69, Q × f 0 = 69,300 GHz and τ f = −58.3 ppm/°C, which was sintered at 1520°C for 3 h in air.