Effect of the composition and structure on the optical properties of Ba1-xLaxTi1-xFexO3 (0 ≤ x ≤ 1) solid solution: Correlation study using Rietveld refinement

In this work, X-ray diffraction assisted with Rietveld refinement method was used to study the effect of the composition on the structural transitions and the optical properties of perovskite ABO3-type, prepared using the conventional solid state reaction technique. X-ray analysis indicates the ability of BaTiO3 to accommodate different percentages of La3+ cation in A-sites and Fe3+ cation in B-sites while maintaining the ABO3-type structure. Rietveld refinement method showed the existence of several phase transitions: a first from tetragonal (0 ≤ x ≤ 0.25) to cubic (0.3 ≤ x ≤ 0.6) and a second from cubic (0.3 ≤ x ≤ 0.6) to orthorhombic (0.7 ≤ x ≤ 1), with one tetragonal sub-transition (P4mm → P4/mmm) and one orthorhombic sub-transition (Pnma → Pbnm). The UV–vis analysis showed that BaTiO3 absorption band undergoes an expansion up to 592 nm as the amount of La3+ and Fe3+ increases. The structural investigation revealed that BOB bond angle has an effect on the band gap values as small values were found for bonds angles close to 180°. As the amount of the substitution increases, a shift of both the conduction band minimum and valence band maximum was observed for all the compositions, which is consistent with the band gap values obtained. •Synthesis and characterization of Ba1-xLaxTi1-xFexO3 (0≤x≤1) solid solution.•Demonstration of two main structural phase transition in BLTF (0≤x≤1) system.•Observation of the optical absorption expansion from the UV domain up to 592 nm of the visible domain.•The reveal of B-O-B bond angle parameter effect on the decrement of the optical band gap.•Visualization of a downward shift of the CBM and upward shift of the VBM.