Electrical properties of BaTiO3-based capacitors are investigated. A new model is developed to explain the frequency response of the impedance of grain-boundary barrier layer (GBBL) capacitors. This model takes into consideration the dipole polarization effect and provides a simple and effective approach to evaluate the performance of GBBL capacitors with various dopants and sintering in different atmospheres. When sintered in a reducing atmosphere, doped BaTiO3 exhibits a higher dielectric constant and a relatively stable dieletric constant with respect to the frequency response and temperature dependence. Also, smaller grain resistivity is obtained with addition of both Dy2O3 and Nb2O5.