Doping behaviors of NiO and Nb2O5 in BaTiO3 and dielectric properties of BaTiO3-based X7R ceramics

Doping behaviors of NiO and Nb2O5 in BaTiO3 in two doping ways and dielectric properties of BaTiO3-based X7R ceramics were investigated. When doped in composite form, the additions rendered higher solubility than that doped separately due to the identical valence between the complex (Ni1/32+Nb2/35+)4+ and Ti4+. NiO–Nb2O5 composite oxide was more effective in broadening dielectric constant peaks which was responsible for the temperature-stability of BaTiO3 ceramics. A reduction in grain size was observed in the specimens with 0.5–0.8 mol% NiO–Nb2O5 composite oxide, whereas the abnormal growth of individual grains took place in the 1.0 mol% NiO–Nb2O5 composite oxide-doped specimen. When the specimen of BaTiO3 doped with 0.8 mol% NiO–Nb2O5 composite oxide was sintered at 1300 °C for 1.5 h in air, good dielectric properties were obtained and the requirement of (EIA) X7R specification with a dielectric constant of 4706 and dielectric loss lower than 1.5% were satisfied.