Using a linear voltage ramp method, ultraslow dielectric relaxation processes of La‐doped BaTiO3boundary layer (BL) capacitors are measured at room temperature. For the electric polarization model of a double‐layer dielectric, a procedure to calculate the electrical parameters of grain and grain boundary has been developed. Calculated results suggest that there is a shell on the surface of the grain. TEM images of the BL capacitor also show a lot of microregions with minor structural modifications. Relaxation times are estimated from the equivalent circuit and are in agreement with fitted resu