A Novel, Simple and Highly Efficient Route to Obtain PrBaMn₂O_5+δ Double Perovskite: Mechanochemical Synthesis

In this work, a mechanochemical route was proposed for the synthesis of the PrBaMn₂O_5+δ (PMBO) double layered perovskite phase. The mechanochemical reaction between Pr₆O₁₁, BaO₂, and MnO powders with cationic stoichiometric ratios of 1/1/2 for Pr/Ba/Mn was performed using high-energy milling conditions in air. After 150 min of milling, a new phase with perovskite structure and cubic symmetry consistent with the A-site disordered Pr_0.5Ba_0.5MnO₃ phase was formed. When this new phase was subsequently annealed at a high temperature in an inert Ar atmosphere, the layered PrBaMn₂O_5+δ phase was obtained without needing to use a reducing atmosphere. At 1100 °C, the fully reduced layered PrBaMn₂O₅ phase was achieved. A weight gain was observed in the 200-300 °C temperature range when this fully reduced phase was annealed in air, which was consistent with the transformation into the fully oxidized PrBaMn₂O₆ phase. The microstructural characterization by SEM, TEM, and HRTEM ascertained the formation of the intended PrBaMn₂O_5+δ phase. Electrical characterization shows very high electrical conductivity of layered PBMO in a reducing atmosphere and suitable in an oxidizing atmosphere, becoming, therefore, excellent candidates as solid oxide fuel cell (SOFC electrodes).