Structural and dielectric properties of B2O3/Li2O-added Ba0.6Sr0.4TiO3 multilayer ceramics for tunable devices

Abstract

B2O3 and Li2O (B/L)-added Ba0.6Sr0.4TiO3 (BST) ceramics sintered at 940 degrees C exhibited a dense microstructure with large grains. The amount of B/L additive was 4.5 wt% with a B/L ratio of 1.5:1. The B/L-related liquid phase assisted the densification of the BST ceramics. This BST ceramic displayed a large dielectric constant (epsilon(r)) of 2834 with a low dielectric loss (tan delta) of 0.21% at 1.0 MHz. It also displayed a large tunability (28.2% at 10 kV/cm) and a high figure of merit (FOM) of 134. BST thick-films were synthesized using the tape casting method. The thick-film densified at 940 degrees C exhibited a large tunability of 18.7% at 10.0 kV/cm and an FOM of 208; these are higher than the values reported in the literature. Multilayer ceramics (MLCs) consisting of five layers of 40-mu m-thick BST thick-films and Ag electrodes were also fabricated at 940 degrees C. No diffusion occurred between the Ag electrode and BST thick-film. A large tunability of 67.6% at 52 kV/cm with a high FOM of 294 was obtained from this MLC. This verified that the B/L-added BST ceramic is effective for application in tunable multilayer devices.