An in-situ neutron diffraction study of the crystal structure of PrBaCo2O5+δ at high temperature and controlled oxygen partial pressure

Defect formation in double perovskites PrBaCo2−xCuxO5+δ at elevated temperatures

“…The discontinuity Δδ of the plots equals nearly 0.04 and 0.01 for x = 0 and 0.5, respectively. Similar features were also observed in work [38] where Δδ was about 0.05 at 850°C and log p O 2 À Á = − 2.26. Neutron diffraction data for PrBaCo 2 O 5+δ after reducing treatment evidence small admixtures (less than 1wt.%) of cobalt oxide CoO [38].…”

“…Similar features were also observed in work [38] where Δδ was about 0.05 at 850°C and log p O 2 À Á = − 2.26. Neutron diffraction data for PrBaCo 2 O 5+δ after reducing treatment evidence small admixtures (less than 1wt.%) of cobalt oxide CoO [38]. Taking into account these results and the earlier data [39] we suppose that the air synthesized samples contain undetectable by X-raying trace amounts of Co 3 O 4 so that their reduction to CoO slightly warps the shape of the isotherms.…”

“…It is known [38,40] that cobaltite PrBaCo 2 O 5+δ acquires tetragonal structure (s.g. P4/mmm) at temperatures above 500°С and oxygen pressures below 0.1 atm. Hence, the non-stoichiometry data in Fig.…”

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

“…Interestingly, chemical lattice strain caused solely by oxygen vacancies formation was found to be anisotropic in double perovskites [5,6] with expansion in ab-plane due to decrease of cobalt oxidation state [5,6] and contraction along c-axis due to the high concentration of oxygen vacancies localized in rare-earth-oxygen-(REO-) plane, which prompts shifts in Co and O positions towards the REO-plane [6]. In the case of cobalt deficient double perovskite EuBaCo 2−x O 6− , however, it seems that cobalt oxidation state, and, as a consequence, its mean size (radius), remains unchanged due to cobalt vacancies formation.…”

“…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.…”