Structure and microwave dielectric behaviour of low-temperature-fired Li₂Zn_1−xCo_xTi₃O₈ (x = 0–0.07) ceramics for low temperature co-fired ceramic applications

Low-temperature-fired Li₂Zn_1−xCo_xTi₃O₈ (x = 0, 0.03, 0.04, 0.05, 0.06, 0.07) ceramics with 1.5 wt% Li₂O–B₂O₃–SiO₂–CaO–Al₂O₃ (LBSCA) glass as sintering aid were attained through a traditional solid-state-reaction method, and the relationship between their structures and microwave dielectric properties were thoroughly investigated. X-ray diffraction patterns revealed that the solid solutions composed of Li₂ZnTi₃O₈ and Li₂CoTi₃O₈ were produced. The main peaks were identified with the cubic spinel phase of the Li₂(Zn,Co)Ti₃O₈. Co substitution successfully lowered the sintering temperature of Li₂ZnTi₃O₈ to approximately 900 °C and accelerated its densification when LBSCA glass was used as the sintering aid. The cobalt content considerably influenced grain homogeneity, grain size and dielectric polarizability, as well as the variation in relative permittivity (ε_r) and quality factor (Q × f). When x = 0.04, Li₂Zn_0.96Co_0.04Ti₃O₈ ceramic sintered at 900 °C had the most uniform grain size and exhibited optimum microwave dielectric properties, having a relative permittivity of 21.61, Q × f of 79,100 GHz and temperature coefficient of resonance frequency (τ_f) of − 12.3 ppm/°C. Thus, it showed potential for low temperature co-fired ceramic applications.