New RMnO3+δ (R=Y, Ho; δ≈0.35) phases with modulated structure

International audienceA series of hexagonal RMnO3 (R=Y, Ho-Lu) compounds are first annealed in various highly oxidizing conditions to show that for the largest R constituents, Y and Ho, it is possible to load the phases with large amounts of excess oxygen. Within the oxygen-annealed samples we identify new heavily-oxygenated phases, that is, YMnO3.35 and HoMnO3.34. The former is then thoroughly characterized by thermogravimetric analysis, X-ray diffraction and electron diffraction. These studies evidence a hexagonal sub-cell (aS≈3.578 Å (aH/3), cS≈11.18 Å, space group P63mc) and satellites, associated with two modulation vectors q→∗1≈0.41a→∗s+0.41b→∗ s+1/3c→∗s and q→∗2=(1/2). The results are interpreted by the formation of a modulated composite structure, resulting from the evolution of the hexagonal parent YMnO3+δ structure toward a reduced pyrochlore-type structure Y2Mn2O7-x, in long- and short-range ordering. © 2014 Elsevier Ltd. All rights reserved

New RMnO3+δ (R=Y, Ho; δ≈0.35) phases with modulated structure

A series of hexagonal RMnO3 (R=Y, Ho-Lu) compounds are first annealed in various highly oxidizing conditions to show that for the largest R constituents, Y and Ho, it is possible to load the phases with large amounts of excess oxygen. Within the oxygen-annealed samples we identify new heavily-oxygenated phases, that is, YMnO3.35 and HoMnO3.34. The former is then thoroughly characterized by thermogravimetric analysis, X-ray diffraction and electron diffraction. These studies evidence a hexagonal sub-cell (aS≈3.578 Å (aH/3), cS≈11.18 Å, space group P63mc) and satellites, associated with two modulation vectors q→∗1≈0.41a→∗s+0.41b→∗ s+1/3c→∗s and q→∗2=(1/2). The results are interpreted by the formation of a modulated composite structure, resulting from the evolution of the hexagonal parent YMnO3+δ structure toward a reduced pyrochlore-type structure Y2Mn2O7-x, in long- and short-range ordering. © 2014 Elsevier Ltd. All rights reserved