Low loss and good chemical compatibility with silver electrodes of Cu2+-substituted Ba3Ti4Nb4O21 ceramics realizing low temperature co-fired ceramics technology: Crystal structure, vibration modes and chemical bonds studies

Abstract

New low loss and low-sintering temperature co-fired Ba3-xCuxTi4Nb4O21 (BCTN, 0 ≤ x ≤ 0.12) ceramics with 0.60 wt% Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass were prepared by solid-state reaction methodology. This work showed that CuO and LBSCA were effective sintering aid, which improved the densification and decreased sintering temperature. Thus, the excellent microwave dielectric properties of BCTN ceramics (x = 0.08) were obtained after sintering at 925 ℃ with εr ~ 44.18, Q×f ~ 17,860 GHz (@ 5.6 GHz) and τf ~ 94.76 ppm/℃. Q×f value was increased nearly 3-fold compared to pure BTN ceramics (~ 6090 GHz). Based on the P-V-L bond theory, the Ti-O and Nb-O bonds together contributed greatly to εr. The Nb-O bonds was the main factor affecting the internal loss on Q×f. The τf closely related to the oxygen octahedron [Ti1/Nb1O6]. The BCTN ceramics would not react with Ag electrodes, and had great potential to be used in LTCC microwave devices.