Synthesis, Structure, and Properties of La₂NiO_4+δ

Abstract

An overview of literature covering the preparation and characterization of La 2 Ni0 4+ g is presented in view of the close relationship to the layered cuprates. Particular emphasis is placed on the sensitive dependence of structure and physical properties on die concentration of excess lattice oxygen, S. The La 2 Ni0 4+ £ phase diagram exhibits structural, antiferromagnetic and metal/insulator phase transitions and at contains at least one phase separation region, similar to the La 2 Cu0 4+ g system. Whereas the structure and magnetic properties of the stoichiometric composition are reasonably well established, significant discrepancies exist with regard to the evolution of behavior with increasing oxygen content.The extraordinary worldwide interest in high-7"c superconductivity, as manifested in La 2 . x (Sr,Ba) x Cu0 4 and other layered systems, has sparked renewed interest in the physical properties of their closely related nickel analogs. In this article we offer a brief review of the preparation, structure, and physical properties of La 2 Ni0 4+ £; due to space limitations it was not possible (except in a few instances) to extend the discussion to alloy systems such as La 2 . x (Sr,Ba) x Ni0 4 , or to other rare earth materials of composition Ln 2 Ni0 4 . Research on the structure and physical properties of the layered perovskites of nickel was pursued at a relatively low level of effort through the early eighties, but has significantly accelerated in last few years. Earlier reviews, particularly in the context of relating lanthanide nickelates to other oxides possessing the K 2 NiF 4 structure, have been published

Oxygen and strontium codoping ofLa2NiO4: Room-temperature phase diagrams

“…Details of crystal growth, O-annealing, and chemical analysis are described in Ref. 1,33,36,37,38. Synchrotron x-ray powder diffraction patterns at room temperature were collected at beamline X7A of the National Synchrotron Light Source at Brookhaven using a Ge(111) monochromator at wavelengths λ of 0.66Å, 0.7Å, or 0.8Å.…”