Structural and Magnetic Studies of Ordered Oxygen-Deficient PerovskitesLnBaCo2O5+δ, Closely Related to the “112” Structure

Synthesis, Single Crystal Growth, and Properties of Cobalt Deficient Double Perovskite EuBaCo2−xO6−δ (x = 0–0.1)

“…Double perovskites LnBaB 2 O 6− (Ln = rare-earth element, B = 3d element) with layered structure, which consists of alternating perovskite layers containing either rare-earth elements or Ba [1][2][3], have already received great attention in past decades due to their fast oxide ion transport, high mixed ionic and electronic conductivity, and high catalytic activity with respect to the oxygen reduction [2][3][4][5][6]. The double cobaltites LnBabo 2 O 6− are of particular interest due to diverse physical properties of cobalt ions [4,[7][8][9], which may exist not only in different oxidation states: Co 2+ , Co 3+ , and Co 4+ , but also in different spin states, and may have several coordination environments, such as tetrahedral, octahedral, square pyramidal, and trigonal pyramidal.…”

“…This large oxygen deficiency is accommodated mostly by the formation of oxygen vacancies in the layers containing rare-earth ions. Depending on pO 2 (oxygen content) and temperature an ordering of oxygen vacancies may occur and, consequently, different superstructures lowering the symmetry of the crystal lattice may be observed as well [1]. As an example, Figure 1 shows the unite cell of EuBaCo 2 O 5.5 with the most typical ordering of oxygen vacancies when they are regularly alternating with occupied oxygen positions along the b-axis of the cell.…”

“…As a result, cell parameter b is doubled as compared to disordered state. Thus the lattice of the oxide has orthorhombic symmetry with s.g. Pmmm when oxygen vacancies are ordered or tetragonal symmetry with s.g. P4/mmm when they are disordered [1].…”

“…It should be emphasized that, up to now, only influence of the oxygen deficiency on the crystal structure and properties of double perovskites was studied [1][2][3][4]10] while both their cationic sublattices are assumed to be stoichiometric. However, according to our preliminary study double perovskites may accommodate significant (up to 0.1) cation understoichiometry in their lattice.…”

Crystal structure and oxygen content of the double perovskites GdBaCo2−Fe O6−δ

“…Mixed ionic and electronic conducting oxides AA 0 Co 2 O 5 , where A is a rare earth element (RE), A 0 -Ba, with double perovskite structure have received great attention in past decade [1][2][3][4] due to their unique magnetic and transport properties at relatively low temperatures. In particular, GdBaCo 2 O 6 À d was shown to possess sufficiently high oxygen ionic conductivity and oxygen chemical diffusion coefficient at temperatures as low as 400 1C [3].…”