Doping behaviors of NiO and Nb_2O_5 in BaTiO_3 and dielectric properties of BaTiO_3-based X7R ceramics

摘要

Doping behaviors of NiO and Nb_2O_5 in BaTiO_3 in two doping ways and dielectric properties of BaTiO_3-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 (Ni_(1/3)~(2+)Nb_(2/3)~(5+))~(4+) and Ti~(4+). NiO-Nb_2O_5 composite oxide was more effective in broadening dielectric constant peaks which was responsible for the temperature-stability of BaTiO_3 ceramics. A reduction in grain size was observed in the specimens with 0.5-0.8 mol% NiO-Nb_2O_5 composite oxide, whereas the abnormal growth of individual grains took place in the 1.0 mol% NiO-Nb_2O_5 composite oxide-doped specimen. When the specimen of BaTiO_3 doped with 0.8 mol% NiO-Nb_2O_5 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.