Tailoring Oxygen Content on PrBaCo₂O₅₊_δ Layered Cobaltites

Abstract

The LnBaCo2O5+δ cobaltites with ordered A-site cations exhibit a very rich phase diagram as a function of the oxygen content, which determines the doping of CoO2 planes. By means of thermogravimetry analysis (TGA), we study the appropriate way to tailor oxygen contents in PrBaCo2O5+δ compounds. Starting from an air-synthesized sample, we study the evolution of δ during different heat treatments with “in situ” TGA measurements. We find that δ can be tailored from δ ≃ 0.2 to δ ≃ 0.9. Thermogravimetry measurements also show that oxygen ions can flow through (0 0 1) PrOδ planes at relatively low temperatures (200 °C, this temperature increases in compounds with smaller rare earths). By means of neutron powder diffraction at room temperature, we determine the structural details and study the eventual order of oxygen vacancies for different values of δ.