Effect of nanometer barium titanate powders on the dielectric properties of X7R ceramics

High dielectric constant X7R dielectric materials were prepared by doping with nanometer BaTiO₃ additives, with a dielectric constant as high as 5,400 and dielectric loss lower than 1.0% at 25 °C, when they were sintered at 1,240 °C for 4 h. The effects of nanometer BaTiO₃ additives on the microstructure and dielectric properties of X7R ceramics were investigated in this paper. The nanometer BaTiO₃ additives were prepared by sol–gel method with an average particle size of ~65 nm. It was favorable by nanometer BaTiO₃ additives to make the ceramics hold high dielectric constant and still satisfy the requirement of EIA X7R specification. Due to the special nano-effect of the nanometer BaTiO₃ additives, the densification of ceramics were promoted effectively, which resulted in the increase of dielectric constant. The temperature-capacitance characteristics which satisfied X7R specification were attributed to the formation of abundant “core–shell” structure, which gave rise to the abundant spontaneous polarization microarea and the decrease of the tetragonality (c/a ratio).