Loss mechanisms and domain stabilisation in doped BaTiO3

Abstract

The ferroelectric and dielectric properties of La, Sr, Zr, Fe and Mn doped BaTiO₃ ceramic are measured within wide limits of the amplitude E_{approximately} of the external electrical AC field. At sufficiently low E_{approximately} the losses are not ferroelectric in origin but are rather determined by the low frequency relaxational response of the material, which is influenced by doping. In the ferroelectric phases a well defined threshold E_{approximately} ⁰ exists at any composition such that the permittivity and the loss factor are independent of E_{approximately} for E_{approximately} E_{approximately} ⁰ due to domain wall motions and reversal of the spontaneous polarisation P_s.E_{approximately} ⁰ is less than 20 V cm^-1 in La doped BaTiO₃ and is up to 5000 V cm^-1 in Fe or Mn doped samples. Compositions with large E_{approximately} ⁰ show constricted hysteresis loops which are described by an internal bias field E_i. In Mn doped BaTiO₃ both E_{approximately} ⁰ and E_i are increased by annealing at low partial pressures of oxygen, E_i and E_{approximately} ⁰ are a measure of the stability of the domain configuration established during ageing below the temperature of the para-electric to ferro-electric phase transition.