Variations in electrical properties of Nb-doped SrTiO3 with cation nonstoichiometry

Abstract

The influences of Sr/(Ti+Nb) ratios on the electrical properties of Nb-doped SrTiO3 ceramics have been investigated. Regardless of Sr/(Ti+Nb) ratios, the appearance of non-linearity in the current-voltage characteristics was observed. When Sr/(Ti+Nb) ratio is lower than 1.000, the results acquired from impedance analysis revealed that the activation energies for carrier conduction were determined to be 0.83 eV in grains and 1.67 eV in grain boundaries. Otherwise, the specimens with Sr/(Ti+Nb) greater than or equal to1.004 showed energies of 0.80 eV in grains and 1.27 eV in grain boundaries. From these measured results, it was suggested that the activation energies, about 0.80 eV, measured in grains were originated from oxygen vacancies and the activation energies, 1.27 and 1.67 eV, measured in grain boundaries were from titanium and strontium vacancies, respectively.