Crystal structure and microwave dielectric properties of temperature stable (CoxZn1–x)TiNb2O8 ceramics

Abstract (Co x Zn 1– x )TiNb 2 O 8 ( x = 0.2–0.8) microwave dielectric ceramics were synthesized via the conventional solid‐state reaction route, and the correlation of microwave dielectric properties on the crystal structure was discussed. Crystal structures of ceramic samples were systematically investigated by X‐ray powder diffraction. Moreover, composition‐induced phase transitions were confirmed via the following sequence: for x ≤ 0.2, single‐phase orthorhombic ixiolite (ZnTiNb 2 O 8 ) was formed, whereas for 0.3 ≤ x <0.8, ixiolite and rutile coexisted. When x ≥ 0.8, only single‐phase rutile was detected. For the (Co x Zn 1– x )TiNb 2 O 8 ceramics, the microwave dielectric properties were changed with the crystal structural transitions: the dielectric constant ( ε r ) and the temperature coefficient of resonant frequency ( τ f ) increased upon increasing the Co 2+ , but the quality factor ( Q ) decreased. A near‐zero τ f = +1.6 ppm/°C was obtained in the Co 0.38 Zn 0.62 TiNb 2 O 8 ceramics with ε r = 40.7 and high Q × f = 16 790 GHz. These research outcomes are expected to have great significance for developing microwave dielectric ceramics in practical applications.