Investigation of crystal structure of SrLa(FeTi)O 6 and BaLa(FeTi)O 6 perovskites by rietveld refinement

Abstract

The structures of the recently reported ordered perovskites SrLa(FeTi)O 6 and BaLa(FeTi)O 6 have been revisited using Rietveld analysis of the powder x-ray diffraction data.Our studies clearly show that earlier authors have incorrectly reported the tetragonal structure in the I4/m space group for SrLa(FeTi)O 6 and the cubic structure in the Fm3 m space group for BaLa(FeTi)O 6 . The correct structure is found to be orthorhombic in the Pnma space group for SrLa(FeTi)O 6 while cubic in the Pm3 m space group for BaLa(FeTi)O 6 . Thus the BaLa(FeTi)O 6 is not an ordered double perovskite as the occupancies of Ba/La ions at A-site and Fe/Ti ions at B-site are disordered resulting in the primitive cubic unit cell in the Pm 3 m space group.Similarly, the occupancies of Sr/La ions at A-site and Fe/Ti ions at B-site are disordered in SrLa(FeTi)O 6 also, ruling out the ordered perovskite structure.

Structural Characterization of B-Site Ordered Ba2Ln2/3TeO6 (Ln = La, Pr, Nd, Sm, and Eu) Double Perovskites and Probing Its Luminescence as Eu3+ Phosphor Hosts

“…Thus we concluded the monoclinic (P2 1 /n) symmetry of these double perovskites. 44,46 The crystal structure derived from the Raman spectra of Ba 2 Ln 2/3 TeO 6 (Ln = La, Pr, Nd, Sm, and Eu) is thus confirmed by Rietveld refinement of the XRD patterns. All the patterns were fitted using the monoclinically distorted unit cell with P2 1 /n symmetry.…”

Structural, morphological, dielectric and optical properties of double perovskites RBaFeTiO6 (R = La, Eu)

“…Furthermore, the crystal parameters obtained for the LaBaFeTiO 6 phase are consistent with those reported in the literature. 18 …”

“…Based on the literature survey, there are only two papers concerning the double perovskite LaBaFeTiO 6 , which cover the structural analysis and magnetic study by Mössbauer spectroscopy. 18,19 These studies revealed that this material crystallizes in a Pm 3̄ m cubic symmetry with a disordered distribution of Fe/Ti ions on the B-sites. 18 In addition, Mössbauer spectroscopic measurements (at 80 K and 300 K) pointed to the paramagnetic feature of this double perovskite with a trivalent high spin state for the iron ions.…”

“… 18,19 These studies revealed that this material crystallizes in a Pm 3̄ m cubic symmetry with a disordered distribution of Fe/Ti ions on the B-sites. 18 In addition, Mössbauer spectroscopic measurements (at 80 K and 300 K) pointed to the paramagnetic feature of this double perovskite with a trivalent high spin state for the iron ions. 19 However, the Eu-based system EuBaFeTiO 6 has not yet been investigated.…”

“…Furthermore, the crystal parameters obtained for the LaBaFeTiO 6 phase are consistent with those reported in the literature. 18 The structure and stability of double perovskites RBaFeTiO 6 can be approximated using the ratio of R 3+ /Ba 2+ -O 2À to Fe 3+ / Ti 4+ -O 2À bond lengths as the tolerance factor (t):…”