Mn–Nb co-doping in barium titanate ceramics by different solid-state reaction routes for temperature stable and DC-bias free dielectrics

Abstract

BaTi1-2xMnxNbxO3 (x = 0, 0.05 and 0.10) ceramics were fabricated by either one-step calcination or two-step calcination with the first calcination of BaTi1-2xMnxO3-δ and the second calcination with Nb2O5 addition, and the effect of the calcinations on crystal structure, microstructure, and electrical properties was investigated. With the Mn and Nb substitution, the crystal system of BaTiO3 changed to a pseudo-cubic, the temperature dependence of the dielectric constant was flattened, and the polarization-electric field (P-E) loops became almost linear. At x = 0.10, compared with the one-step calcined ceramics with a remaining hexagonal phase and higher dielectric loss at high temperatures, the two-step calcined ceramics had a single-phase perovskite structure, the dielectric constants of 575–345 at temperatures between 25 and 150 °C with smaller dielectric loss, and the dielectric constants estimated from the slopes of the P-E loop of ∼650 at 0 kV/cm and ∼500 at 100 kV/cm at room temperature. BaTiO3+xMnO2+x/2Nb2O5 ceramics were also fabricated at x = 0.05 and 0.10, but they were less dense and had a secondary phase. These results suggest that the two-step calcined BaTi1-2xMnxNbxO3 ceramics with x = 0.10 can be a candidate material for temperature stable, DC-bias free capacitor applications.