Bipolaron dynamics in pure and doped SrTiO3 and KTaO3 perovskite systems

The dielectric relaxation in SrTiO3, Sr0.942Ca0.058TiO3, and K0.989Li0.011TaO3 was analyzed. While at higher temperatures the characteristic relaxation frequency follows the Arrhenius behavior, its value is temperature independent at low temperatures. It is shown that such a behavior is a consequence of the dynamic properties of bipolarons, which undergo a transition from thermally activated hopping to a tunneling regime. (C) 2002 American Institute of Physics.