Adjustable microwave dielectric properties of ZnO-TiO2-ZrO2-Nb2O5 composite ceramics via controlling the raw ZrO2 content and sintering temperature.

A series of 2.5ZnO-(5−x)TiO₂-xZrO₂-2.5Nb₂O₅ (abbreviated as ZTZN, 0.2 ≤ x ≤ 0.4) composite ceramics were prepared by a solid state reaction method. The phase composition and microwave dielectric properties of the ceramics were investigated. X-ray diffraction patterns displayed the coexistence of ZnTiNb₂O₈ and Zn_0.17Nb_0.33Ti_0.5O₂ phases. With increasing the sintering temperature, the bulk density (ρ), permittivity (ε_r) and temperature coefficient of resonator frequency (τ_f) increased. With increasing the ZrO₂ content, the ρ firstly increased and then decreased, Q × f value increased, ε_r and τ_f value decreased. Importantly, the τ_f value of ZTZN ceramics (0.2 ≤ x ≤ 0.4) could be adjusted to near-zero. The 2.5ZnO-4.7TiO₂-0.3ZrO₂-2.5Nb₂O₅ ceramics sintered at 1075 °C exhibited the best comprehensive performances of Q × f = 30,155 GHz, ε_r = 44 and τ_f = 0.89 ppm/°C, indicating that they are candidates for microwave devices. [ABSTRACT FROM AUTHOR]