Excess oxygen ordering in the La_2NiO_(4+δ) system studied by low-frequency internal friction

摘要

Different elastic spectra were found for La_2NiO_(4+δ) in the three ranges: δ < 0.110, 0.110 < δ < 0.145, and δ> 0.145. It is concluded that for 0.110< δ < 0.145 the low-temperature phase consists of phases with three-dimensional (3D) ordering and one-dimensional (1D) ordering of interstitial oxygen; the change of the ordering state of excess oxygen from 1D to 3D with increasing oxygen content is not abrupt but smooth; and for δ > 0.145 all excess oxygen is three-dimensionally ordered. A model of the 3D ordering clusters for 0.110 < δ < 0.145 is discussed. Glass transitions of the interstitials and glass dynamic phenomena were also observed.