Role of morphology, crystal orientation and stoichiometry in the electrical response of perovskite EuTiO3 ceramics

To identify the generation of various contributions in the electrical response of EuTiO3, a series of pure and doped, morphologically different and crystallographically oriented thin films prepared through RF magnetron sputtering and polycrystalline samples prepared through solid state reaction method have been investigated. Effect of stoichiometry, morphology and crystallographic orientation on the electrical response have been traced. Interestingly, in case of thin films, synthesis in more reducing atmosphere led to an in-plane crystallographic re-orientation from [110] to [100], accompanied by the observation of a prominent intrinsic antiferrodistortive phase transition. At temperatures above the antiferrodistorive phase transition, potential barriers to conduction at grain boundary are found to be directly proportional to the oxygen vacancy concentration, and inversely proportional to the average grain size. The relaxation times obtained from the frequency dependent dielectric response show an anomalous non-monotonic variation with temperature, which arises due to the variation of octahedral tilt angle.