Probing structural distortions in rare earth chromites using Indian synchrotron radiation source

Abstract

Effect of R site ionic radius on the structural distortions in RCrO3(R: La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Y) rare earth perovskite chromites is investigated through synchrotron based X-ray diffraction technique. The said structural distortions are measured in the terms of CrO bond lengths, CrO6octahedral tilt, tolerance factor (t) and RO12polyhedral distortion. It is observed that the lattice parameters (b and c), RO bond length, tolerance factor and Cr–O–Cr bond angle increases with increase in the radius of R site ion; whereas octahedral tilts (along [010] and [101]) and RO12polyhedral distortion decreases with increase in the radius of R site ion. Further it is observed that the radius of R site cation does not have significant effect on lattice parameter ‘a’ and CrO bond length (hence on the distortion of CrO6octahedra). A comparison of the crystal structure parameters obtained using refinement of synchrotron powder X-ray data and that estimated theoretically using modern bond valence parameters (SPuDS) has been carried out. A one to one correlation between the experimental and theoretical results has been observed. © 2016, Indian Association for the Cultivation of Science.