Internal bias in ferroelectric ceramics: Origin and time dependence

Abstract The internal bias field which is observed in many ferroelectric materials is explained semiquantita-tively. Dipolar defects in the ferroelectric cause div P # O at the defect sites. The electric fields diverging at these sites tend to orient the dipoles to energetically favourable orientations. The free energy is modified by this effect in a similar way as by an electric field. The transient relaxation of the dipoles to the new equilibrium is treated and describes well the observed time behaviour of the internal bias.