Influence of oxygen vacancies on the EPIR effect in Nd0.7Sr0.3MnO3 ceramics

Nd0.7Sr0.3MnO3 polycrystalline ceramic samples (NSMO) were synthesized by solid state reaction with a post annealing for parts of samples under different partial pressures of oxygen at 1350 °C for 12 h. XRD shows that all the samples are in single phase with a perovskite structure. The electrical transport measurement implies that the oxygen concentration has an important influence on the electrical pulse induced resistance, i.e. the EPIR-effect, for NSMO samples. For the oxygen-enriched sample, which probably contains a smaller amount of oxygen vacancies, the I-V characteristic is linear with a very small resistance, and the EPIR-effect is not detectable within the experimental accuracy. However, after sintered and annealed in reducing atmospheres, an EPIR effect appears and even becomes stronger and more stable if the sintering atmosphere is more reducing than that of normal air condition. Besides, the I-V becomes nonlinear and the initial resistance increases with increasing deficiency of oxygen, which means that the oxygen vacancies and their deep level trap states play an important role for the EPIR effect of NSMO. In this manuscript, an oxygen vacancy trapped state model is put forward to explain the relation between oxygen concentration and the EPIR effect.