Crystal Structure Refinement and Stability of LaFexNi1−xO3Solid Solutions

Abstract

The crystal structure refinement of LaFexNi1−xO3(0≤x≤1) solid solutions was determined and analyzed by means of Rietveld refinement from X-ray powder diffraction data. The solid solutions with 0≤x<0.5 are isostructural with LaNiO3and crystallize in the rhombohedral system, space groupR3c, while those with composition 0.5<x≤1 are isoestructural with LaFeO3and crystallize in the orthorhombic system, space groupPnma. All of the solutions are single phase except that with the intermediate composition (x=0.5), where both phases are observed. The cell volume increases with the iron content. This can be ascribed to the larger ionic radius of Fe3+(HS) compared to Ni3+(LS). LaFe0.25Ni0.75O3was found to be single phase when prepared at temperatures as high as 1000°C, indicating an increase in the stability of the perovskite phase at high temperatures when a relatively small amount of iron is substituted for Ni in LaNiO3.