BaCoO_2+δ: a new highly oxygen deficient perovskite-related phase with unusual Co coordination obtained by high temperature reaction with short reaction times

Abstract

A pinch of oxygen: incorporation of small additional oxygen introduces partly square planar coordination into BaCoO2+δ.

Structural, Magnetic and Catalytic Properties of a New Vacancy Ordered Perovskite Type Barium Cobaltate BaCoO2.67

“…From the NYQUIST plot a single depressed semicircle was observed which was fitted using a single R‐CPE (constant phase element). The room temperature conductivity of the sample was determined from the intercept on the X‐axis and calculated to be 2.89×10 −4 S cm −1 which is of the same order of magnitude as that of BaCoO 1.80 (OH) 0.86 [7] and three orders of magnitude higher than that of BaCoO 2+δ [2] . This is in agreement with what is expected from the presence of Co in a mixed oxidation state (+3/+4).…”

“…This is in agreement with what is expected from the presence of Co in a mixed oxidation state (+3/+4). An activation energy of 0.21(1) eV was calculated from the slope of the Arrhenius plot (Figure 4a) indicating the dominance of electronic contribution to overall conductivity [2] …”

“… [1] and Mentré et al. [5] For oxygen rich systems, i. e. for low values of y , hexagonal modifications (2H, 5H, 12H) are known and for higher values of y , the cubic modification or ccp‐ related vacancy‐ordered variants are known (BaCoO 2.22 and BaCoO 2 ),[ 2 , 5 , 6 ] and ccp ‐related arrangements can also be stabilized by the uptake of water (BaCoO 1.80 (OH) 0.86 ). [7] Such or similar barium cobaltates have attracted a lot of attention for their activity for the oxygen evolution reaction (OER).…”

“…An activation energy of 0.21(1) eV was calculated from the slope of the Arrhenius plot (Figure 4 a) indicating the dominance of electronic contribution to overall conductivity. [2] …”

Oxide Ion and Proton Conductivity in Highly Oxygen-Deficient Cubic Perovskite SrSc0.3Zn0.2Ga0.5O2.4

“…Since SSZ40GO is a cubic perovskite, we can write its formula as SrSc 0.3 Zn 0.2 Ga 0.5 O 2.4 . Literature examples of perovskites with oxygen contents lower than ABO 2.5 are uncommon and typically found for compounds containing variable oxidation state transition metals − (e.g., Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ where δ can be up to 1 depending on the p O 2 ) or in compounds like SrCuO 2 and SrFeO 2 which have the square-planar-based infinite layer structure. − These are frequently made by low-temperature topotactic reduction of oxygen-rich phases. On the other hand, Takeda et al reported oxygen deficiency corresponding to the oxygen content of 2.45 (normalized to perovskite) in the Sr/Ba/Sc/Al/O system.…”