Orthorhombic–orthorhombic phase transitions in Nd2NiO4+δ (0.067≤δ≤0.224)

Variation of the phases of Nd2NiO4+δ with the excess oxygen concentration δ has been examined at room temperature in the range 0.067≤δ≤0.224 using the X-ray powder diffraction technique. The phases observed at room temperature are orthorhombic-I (0.21<δ≤0.224), orthorhombic-IV (0.175<δ≤0.21), orthorhombic-II (0.15<δ≤0.175), orthorhombic-II+quasi-tetragonal-I (0.10<δ≤0.15), and quasi-tetragonal-I (0.067<δ≤0.10).

Graphical abstractVariation of (a) the lattice constants and (b) the cell volume at room temperature of Nd2NiO4+δ with the excess oxygen concentration. OI: orthorhombic-I; OII: orthorhombic-II; OIV: orthorhombic-IV; TI: quasi-tetragonal-I.Figure optionsDownload full-size imageDownload as PowerPoint slide