Effect of Bi2O3 doping on the dielectric properties of medium-temperature sintering BaTiO3-based X8R ceramics

Abstract

Medium-temperature sintering X8R ceramics were fabricated based on BaTiO3-based ceramics with Bi2O3 additives. The effects of sintering aids Bi2O3 on crystalline structure and electrical properties of BaTiO3-based ceramics were investigated. The sinterability of BaTiO3 ceramics was significantly improved by adding Bi2O3, whose densification sintering temperature reduced from 1,260 to 1,130 °C. However, the dielectric constant (e) of BaTiO3-based ceramics doped with Bi2O3 was decreased dramatically. Both low e phase Bi4Ti3O12 and the decrease of the tetragonality (c/a ratio), which are demonstrated by XRD pattern, are resulted in the decrease of e. The e of samples doped with 5.5 wt% Bi2O3 was higher than the other doped samples. The substitution of Bi3+ for the Ba2+ in BaTiO3 resulted in the increase of electrovalence (from +2 to +3) of A-site ion, so the attractive force between A and B (Ti4+) sites becomes stronger. Thus Ti4+’s polarization enhances, then e was increased to some extent. The X8R BaTiO3-based ceramics could be sintered at as low as 1,130 °C by doping 5.5 wt% Bi2O3 additives into the BaTiO3-based ceramics, with a e greater than 2,430 at 25 °C, dielectric loss lower than 1.3 % and temperature coefficient of capacitance <±15 % (−55–150 °C).