Anomalous octahedral distortions in LaFe1-xNixO3

Perovskite-type LaFe1-xNixO3 in the composition range with orthorhombic crystal structure (x = 0.0, 0.1, 0.3 and 0.5) was prepared by the standard solid-state reaction method. The phase formation was checked by synchrotron x-ray diffraction. The structure was refined from the collected x-ray diffraction data using the Reitveld refinement method. The synthesized compositions crystallized mainly in the Pbnm symmetry. The available data in the literature on the structural properties and crystal phase evolution of the solid solution series LaFe1-xNixO3 were also analysed critically. We report an anomalous variation in the octahedral deformations in these compositions. In order to explore the composition-dependent microscopic changes driving these structural distortions, we used the refined structural parameters (cell dimensions and atomic coordinates) from our own results and the literature to calculate and see the effects of composition on several structural distortion parameters in an orthorhombic perovskite. Variation of these parameters strongly suggested that incorporation of Ni in LaFeO3 caused the octahedral deformation to increase. However, octahedral tilting decreased with the addition of Ni in LaFeO3. The obtained change in the orthorhombic distortions was caused by the possible presence of Jahn-Teller Fe4+ cations.