Preparation and properties of compounds of the complex metal oxides Y 2BaMO 5 ( M ≡ Cu, Zn) with added hydrogen

Abstract

The complex metal oxides Y 2BaMO 5( M ≡ Cu, Zn) have been found to react directly with H 2 gas to form crystalline hydrogen addition compounds. X-ray diffraction data for H x Y 2BaCuO 5 indicate that the reaction sequence for this oxide consists of the formation of a solid solution phase up to x ≈ 2.1, in which the partial molar volume of H, V ̄ H , is nearly zero, followed by the precipitation of a hydrogen-rich phase. The maximum H 2 uptake achieved to date corresponds to H 3.9Y 2BaCuO 5. Similar diffraction studies of the H x Y 2BaZnO 5 system indicate the presence of a solid solution phase to x = 2.0, which is the maximum hydrogen content so far achieved for this oxide; here V ̄ H is also approximately zero. Neither hydriding reaction is reversible and attempts to remove hydrogen at elevated temperatures lead to the evolution of water and a partial reduction of the compound. IR absorption experiments for the H x (D x )Y 2BaCuO 5 system in the solid solution region indicate that hydrogen (deuterium) is most likely bound to both oxygen and copper. IR studies of H 0.3Y 2BaZnO 5 show the presence of OH (hydroxyl) type bonding only.