Enhanced oxygen mobility by doping Yb in BaGd1-xYbxMn2O5+δ double perovskite-structured oxygen storage materials

Abstract

The A-site ordered BaGd1-xYbxMn2O5+δ double perovskites have been systematically investigated in terms of the crystal structure, oxygen nonstoichiometry, microstructure and oxidation states of Mn, oxygen storage properties and oxygen in-situ intake, as well as transport properties. The increased content of Yb in BaGd1-xYbxMn2O5+δ results in a decrease of the relative unit cell volume changes between oxidized materials and reduced counterparts. Crystal structure with P4/nmm space group is observed at room temperature in all BaGd1-xYbxMn2O5+δ (x = 0, 0.2 and 0.4), except in BaGd0.6Yb0.4Mn2O6. The increased content of Yb in BaGd1-xYbxMn2O5+δ modifies materials' morphology, allowing to obtain fine powders. The Mn2+ and/or Mn3+ oxidation states are present in the reduced BaGd1-xYbxMn2O5, confirmed by XPS studies. The Yb doping in BaGd0.6Yb0.4Mn2O5+δ significantly decreases the reduction time and oxidation/reduction temperature. The in-situ oxidation of BaGd0.6Yb0.4Mn2O5 in air associated with P4/nmm → P-1 space group change occurs between 225 and 275 °C, and its nature may indicate the oxygen diffusion mainly occurs in the Gd0.6Yb0.4 layers. The TEC values calculated from high temperature XRD data, not exceeding 14.8(1) × 10−6 K−1, are moderate. The high electrical conductivity (100 S cm−1 in air at 600 °C) and high oxygen diffusion coefficient suggest wide potential applications of the developed BaGd0.6Yb0.4Mn2O5+δ.