Eur. Phys. J. B 37, 321-327 (2004)
https://doi.org/10.1140/epjb/e2004-00062-8

Structural studies of La_1-xSr_xMnO_3+δ (x = 0.1–1.0)

Inter University Consortium for DAE facilities, University Campus, Khandwa Road, Indore-452 017, India

Corresponding author: ^a bindu@iucindore.ernet.in

Received: 18 July 2003
Revised: 17 November 2003
Published online: 2 April 2004

Abstract

We report here for the first time (particularly for ) a systematic structural study using Rietveld Profile Refinement of powder X-ray diffraction data on the series of polycrystalline compounds LaSr_xMnO (). The iodometric redox titration results show that the compounds and the end compound are oxygen excess and deficient respectively and the compounds in the compositional range are oxygen stoichiometric within the experimental error. It is found that the structure remains hexagonal until x=0.4 composition. On further doping, at x=0.5 composition, a structural transition to orthorhombic phase is observed. Around this composition, very small variations in the Mn-O(2)-Mn and average Mn-Mn bond distances are observed. For above x=0.5, until x=0.8 composition, the structure remains orthorhombic with reduced orthorhombic distortion. For the next compound, x=0.9, a mixed hexagonal and orthorhombic phase is observed where the hexagonal phase is 6 layered with stacking sequence of ABCACB type and the orthorhombic phase is more distorted than that of x=0.8 composition. The end compound is a four layered hexagonal structure with stacking sequence ABAC type which is more distorted than ABCACB type. As one goes down the series, a decrease in the volume per formula unit and average Mn-O bond distance are observed except at x=0.9 composition. The observed structural transitions from hexagonal to orthorhombic to layered hexagonal phase can be explained under the electrostatic limit.