PREPARATION AND INVESTIGATION OF THE PHYSICAL-PROPERTIES OF FLUORINATED ND2-XSRXNIO4+DELTA

Selected members of the Nd2-xSrxNiO4+δ solid solution series were fluorinated by a low temperature ion-exchange reaction. Nd2NiO4.16 is orthorhombic at ambient temperature and shows an increase in the orthorhombic distortion as a result of fluorination. The a unit cell parameter of Nd2NiO4.16-xFy decreases while the b and c cell parameters increase relative to the oxygen rich sample Nd2NiO4.16. The unit cell volume of the fluorinated sample relative to the oxygen rich sample increases. Nd2NiO4.16 undergoes a structural phase transition at 575°C, and the fluorinated analogue shows no evidence of a structural phase transition up to 700°C. The Nd2NiO4.16-xFy phase decomposes at 700°C into Nd2NiO4+δ, NdOF, NdF3, and NiO as determined by differential thermal analysis and X-ray diffraction analysis. The significant changes in the electrical and magnetic properties of fluorinated Nd2-xSrxNiO4+δ compared to the oxide are discussed in terms of structural properties of the NiO basal planes. © 1992.