Ferrimagnetism in the High Pressure 6H‐Perovskite BaCrO₃

Abstract

The 6-layered hexagonal polymorph of BaCrO 3 has been synthesized at 900°C under a pressure of 9 GPa. The hexagonal structure (space group P6 3 /mmc, cell parameters a = 5.3809(9) and c = 13.123(3) Å at 300 K) is stable on cooling down to 5 K. Ferrimagne-

Selective Hydride Occupation in BaVO3–xHx (0.3 ≤ x ≤ 0.8) with Face- and Corner-Shared Octahedra

“…No peaks associated with impurities or superstructures were found. The obtained pattern resembles with those of a 6H-type perovskite structure consisting of alternate stacking of two face-shared octahedral layers and one corner-shared octahedral layer along the hexagonal c axis (Figure a), as found in other transition metal oxides BaTiO 3– d (a high temperature form) and BaCrO 3 . , A QMS measurement upon heating under an argon gas flow revealed a significant amount of H 2 being released at 250–450 °C (Figure S2). A similar H 2 release behavior has been seen in other oxyhydrides including ATi­(O,H) 3 , − BaScO 2 H, and SrCrO 2 H .…”

“…The obtained pattern resembles with those of a 6H-type perovskite structure consisting of alternate stacking of two face-shared octahedral layers and one cornershared octahedral layer along the hexagonal c axis (Figure 2a), as found in other transition metal oxides BaTiO 3−d (a high temperature form) and BaCrO 3 . 29,30 A QMS measurement upon heating under an argon gas flow revealed a significant amount of H 2 being released at 250−450 °C (Figure S2). A similar H 2 release behavior has been seen in other oxyhydrides including ATi(O,H) 3 , 1−3 BaScO 2 H, 15 and SrCrO 2 H. 13 A 5Htype BaVO 3−d (0 ≤ d ≤ 0.2), which consists of alternate stacking of three face-shared octahedral layers and two cornershared octahedral layers (Figure S3), was previously prepared in ambient pressure.…”

Designing Fe-Based Oxygen Catalysts by Density Functional Theory Calculations

“…Co substitution reduces the formation energy substantially compared to that of the pristine BFO. Experimentally, cubic BaVO 3 46 and BaCrO 3 47 can only be obtained under extreme conditions, for example, by high pressure-induced phase transition. In addition, BaMnO 3 48 and BaCoO 3 49 are hexagonal with ordered vacancies.…”

High-pressure BaCrO3 polytypes and the 5H–BaCrO2.8 phase

“…[18] High pressure syntheses used a 2:1 mixture of Ba 3 Cr 2 O 8 and Cr 2 O 3 . Ba 3 Cr 2 O 8 was used to provide excess oxygen pressure to stabilise Cr 4+ , and to avoid introducing carbonate or hydroxide into the high pressure reactions, as these species may have been present in the BaO used for some syntheses by Chamberland [11].…”