Na2CaTi2Ge3O12: An anti-reductive garnet ceramic with high quality factor and chemical compatibility with Cu/Ag electrodes for low temperature co-fired application

Abstract

Microwave dielectric ceramics with excellent properties and low sintering temperatures are pursued saving energy and cofiring with metal electrodes (especially Ag, Cu). Herein, a low-firing Na2CaTi2Ge3O12 garnet was fabricated via a simple solid-state method. XRD, SEM, Raman spectrum, and dielectric characterization were used to reveal the influence of sintering temperature on crystal structure and dielectric properties. A single-phase Na2CaTi2Ge3O12 ceramic densified at 960 °C has the optimized dielectric properties with εr = 15.3 ± 0.2, Q×f = 55,900 ± 2000 GHz, and τf = −15.7 ± 0.5 ppm/°C. The infrared (IR) spectrum was applied to estimate the intrinsic contribution of lattice vibration to microwave dielectric properties. The anti-reductive feature of Na2CaTi2Ge3O12 ceramic was evaluated via sintering at a reducing atmosphere while cofiring with Cu electrodes. The good chemical compatibility with Ag and Cu electrodes manifests the potential prospect of Na2CaTi2Ge3O12 ceramic in the low-temperature co-fired ceramic (LTCC) application.