Influence of CuO additive on phase formation, microstructure and microwave dielectric properties of Cu-doped CuxZn1.8-xSiO3.8 ceramics

Zinc silicate is a promising microwave dielectric material because of its excellent dielectric properties, i.e., low dielectric permittivity ( ε r ) and high quality factor ( Q × f ). Cu x Zn 1.8- x SiO 3.8 ceramics (0 ≤ x ≤ 0.4 with a step of 0.1) were fabricated using a conventional solid-state process, and the Zn-deficient approach was employed to suppress the formation of secondary phases. The X-ray diffraction reveals that Cu 2+ doping does not alter the main crystal structure of Zn 2 SiO 4 but the secondary phase of CuO and SiO 2 is formed when Cu content exceeds solid solubility. Also, the addition of Cu 2+ ions widens the sintering temperature zone, and then reducing sintering temperature by nearly 300 °C. The addition of CuO changes the microstructure of the crystal, but redundant CuO forms the secondary phase and affects the dielectric permittivity of the material. On the other hand, the dielectric permittivity has a linear relationship with the temperature stability coefficient. At x = 0.1 and T = 1010 °C, the quality factor of Cu 0.1 Zn 1.7 SiO 3.8 ceramics reaches a maximum value of 54,128 GHz, while the dielectric properties also attain the optimal level: ε r = 6.70 and τ f = − 29.22 ppm/ °C. It is worth emphasizing that the as-fabricated ceramics can be co-fired with copper electrodes, rendering promise in wireless communication technology.