Influence of the cationic ordering in the dielectric properties of the La 2MnCoO 6 perovskite

Abstract

In this work, we have focused in the influence of the B-site Mn/Co cation ordering on the dielectric properties of the La 2MnCoO 6 perovskite. For this purpose, using different thermal treatments, we have prepared two samples of La 2MnCoO 6 differing in the degree of cation ordering: an almost long-range cationic and valency ordered Mn 4+:Co 2+ 1:1 phase (sample A), and another sample where the presence of the ordered phase gets interrupted by the existence of significant amounts of disordered cation/valency regions (sample B). Very interestingly, the electrical resistance and dielectric properties of these two samples are remarkably different. For example, at 300 K and ν = 10 4 Hz, the dielectric constant, ε ′ r , of the ordered sample is ∼15 while it is much higher in the case of the less ordered material, ε ′ r ∼ 10 5 . We attribute this different behavior to the different electric and electronic characteristics arising from the distinct Mn/Co arrangements and valencies, that in the case of the more disordered sample gives rise to an “intrinsic” Maxwell–Wagner effect responsible for the very high ε ′ r values exhibited at room temperature.