Medium K and temperature-stable Co2+-substituted LiNb0.6Ti0.5O3 microwave dielectric ceramics for LTCC miniaturized applications

Abstract

At present, 5 G communication is developing rapidly, devices are becoming miniaturized, which requires the continuous emergence of materials with high dielectric constant. In this work, choosing Co2+ to substitute Li1–2xCoxNb0.6Ti0.5O3 (LCNT, 0 ≤ x ≤ 0.1) + 0.4 wt% LBSCA ceramics successfully achieved high permittivity εr and temperature stable resonant temperature frequency coefficient τf sintered at 950 ℃, including εr∼62, Q×f∼6255 GHz, and τf∼0.97 ppm/℃ (x = 0.02), εr∼56.55, Q×f∼7090 GHz, and τf∼− 28.07 ppm/℃ (x = 0.06). Meanwhile, the influence of Co2+ on LNT ceramics for phase composition, micro-structure, microwave dielectric performance and Raman vibration had been studied in detail. All samples belonged to M phase. Rod-like or blocky grains were gradually refined, indicating that Co2+ had the effect of grain refinement. In microwave dielectric performance, ionic polarizability played a leading role in εr, Q×f value was positively correlated with the bulk density, τf directly depended on the average repeatable layer N. In Raman spectroscopy, three modes of Raman vibration had been identified as translation or rotation of Li+ ions, Nb/Ti bond vibration, [Nb/TiO6] octahedral vibration. To meet low temperature co-fired applications, the LCNT (x = 0.02) ceramic didn’t react with Ag, which suggested it was achieving candidates for the next generation of medium K LTCC materials.