Synergistic effect of terbium and calcium ions on the temperature stability and dielectric loss of BaTiO3-based ceramics

Abstract

To improve permittivity-temperature stability for BaTiO3 ceramics containing terbium dopant, a new dielectric system (Ba1–xTbx)(Ti1–x/2Cax/2)O3 (x = 0.01–0.20) (BTTC) was prepared at 1400 °C using the conventional mixed-oxide method. The solubility limit of Tb/Ca in BTTC was determined by XRD to be x = 0.12 and BTTC exhibited tetragonal perovskite structures. An abnormal phenomenon was discovered that with increasing x from 0.01 to 0.04 the dielectric peak associated with the orthorhombic-tetragonal phase transition point shifted to low temperatures. The mixed valence states of Tb3+/Tb4+ and mixed A and B occupancy of Tb/Ca2+ in the perovskite lattice were confirmed. BTTC with x = 0.03 and 0.04 satisfied X5R and X4P specifications, respectively, and exhibited some advantageous properties such as higher relative density (ρr = 91 and 93%), lower loss (tan δ = 0.016 and 0.014), higher permittivity (ε′RT = 1820 and 1360), and frequency stability in the range of 1–107 Hz. The point defect chemistry is discussed and the real formula of BTTC is suggested. By comparing BaTiO3 ceramics containing Tb or co-doped with Tb and other rare-earth ions (La, Dy) in many existed works in the dielectric field, the synergistic effect of Tb and Ca in BaTiO3 is more significant and helpful to improve the temperature stability of Tb-related BaTiO3 ceramics or to reduce the dielectric loss in the working temperature region. A small number of B-site Tb4+ in BTTC played a decisive role in the low dielectric loss.