High-Q and near-zero τf composite Li2Mg2TiO5-Sr3(VO4)2 ceramics for low-temperature co-fired ceramic applications

Abstract In the first part of this study, the effects of LiF additives on the phase constitution, microstructure, and microwave dielectric properties (MDPs) of Li2Mg2TiO5 ceramic were studied systematically. The addition of LiF not only effectively lowered the sintering temperature but also considerably improved sinterability and quality factor simultaneously. The Li2Mg2TiO5+4 wt% LiF ceramic sintered at 900 °C for 4 h presented optimum MDPs with er = 14.6, Q × f = 128,500 GHz and τf = -35.6 ppm/°C. Its relatively large negative τf value could be counteracted to near zero by Sr3(VO4)2 for the first time. In the second part of the study, a series of (1-x)[Li2Mg2TiO5+4 wt% LiF]-x[Sr3(VO4)2+1 wt% B2O3] (abbreviated as (1-x)[LMT+4LiF]-x[SV+1B2O3]) (0.25 ≤ x ≤ 0.4) composite ceramics were designed and prepared through the traditional solid-state sintering route. The XRD patterns revealed that Li2Mg2TiO5 and the Sr3(VO4)2 phase could be well coexisted and no impurity phase was detected. A near-zero τf value of -1.6 ppm/°C was obtained in the 0.65[LMT+4LiF]-0.35[SV+1B2O3] ceramic with er of 13.4 and high Q×f of 91,860 GHz. The excellent chemical compatibility of the ceramic with Ag was confirmed through co-firing at 900 °C for 2 h. All results indicate that the composite 0.65[LMT+4LiF]-0.35[SV+1B2O3] ceramic can be applied to low-temperature co-fired ceramic technology.