Dielectric relaxation in doped SrTiO3 : Transition from classical thermal activation to quantum tunnelling

The transition from the thermally activated regime to quantum tunneling is observed in the dielectric relaxation in SrTiO3 ceramic samples doped with Mn and (MgNb). The relaxation is attributed to MnTi4+ off-center ions and to polaronlike defects coupled to MnTi2+ and NbTi5+ centers. The experimental results are fitted to an Arrhenius relation and to quantum tunneling with the account of damping and phonon-assisted processes.