New perovskite materials of the La2−xSrxCoTiO6 series

Abstract

Substitution of La³⁺ by Sr²⁺ in the double perovskite La₂CoTiO₆ yields materials of the La_2−xSr_xCoTiO₆ series showing a significant amount of trivalent cobalt ions when prepared at ambient atmosphere. The as-prepared compounds can be reduced in severe conditions retaining the perovskite structure while inducing the formation of a large amount of oxygen vacancies. The limit of aliovalent substitution in this series was found to extend up to x = 1. For substitution of La³⁺ up to 15% cobalt and titanium are ordered, though the order is progressively lost as x increases; for x ≥ 0.30 no ordering is observed as evidenced by magnetic measurements. The ability of these materials to present either cobalt ions in a mixed oxidation state or large amounts of anion vacancies depending on the atmosphere makes them interesting to be further investigated regarding their electrical and electrochemical properties, and hence, their usefulness in some electrochemical devices.