Effect of stoichiometry on electrical response and polydispersivity related to hopping polarization in EuTiO3

We present a detailed dielectric response of EuTiO3 to identify the role of Eu3+, Ti3+ ions, and oxygen vacancies in the generation of hopping conduction by varying oxygen stoichiometry. The dielectric response clearly reveals a transition from single relaxation to multiple relaxation mechanisms (excluding grain boundary contribution) as a function of a decrease in oxygen content. Systematic evaluation of dielectric and electric responses with the aid of magnetic measurements has been utilized to differentiate between Eu3+ doped EuTiO3 and EuTiO3-δ compounds in least and moderate reducing conditions. A rise in AC conductivity correlates well with the onset temperature of relaxation mechanisms, and the corresponding activation energies calculated through the Arrhenius law indicate that the observed mechanisms are thermally activated charge carrier hopping between Ti ions present in multiple valent states. A schematic model is presented for EuTiO3, and the possible conduction mechanisms are determined consi...