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<p>Rare-earth-based perovskites R(Fe<sub>0.5</sub>Cr<sub>0.5</sub>)O<sub>3</sub> (R = Tb, Yb) have been synthesized by the conventional solid-state reaction method to investigate the influence of the A-site cation size on their structural and optical properties. Rietveld refinement of X-ray diffraction (XRD) data confirmed the formation of a single orthorhombic distorted perovskite phase for both materials. The structural distortion evaluated via different parameters has been correlated with the size variation of the rare-earth elements. An in-depth study of the distortion mechanisms has been conducted through Rietveld analysis. Microstructural evaluations using scanning and transmission electron microscopy (SEM/TEM), alongside Scherrer’s equation and Williamson-Hall analysis, confirmed their highly polycrystalline nature. The evidence of stoichiometry and the homogeneous, random distribution of elements within the compounds was highlighted through energy-dispersive X-ray spectroscopy (EDX) and elemental mapping. Vibrational studies (FTIR and Raman spectroscopy) further supported the structural findings, demonstrating that while overall spectral symmetries remain consistent, the Cr/FeO<sub>6</sub> octahedral tilt angles and bond lengths shift in response to the A-site cation size. Optical property analysis reveals direct band gap energies of 1.90(6) eV for Tb(Fe<sub>0.5</sub>Cr<sub>0.5</sub>)O<sub>3</sub> and 1.93(4) eV for Yb(Fe<sub>0.5</sub>Cr<sub>0.5</sub>)O<sub>3</sub>. Notably, while the tolerance factor decreases from 0.869 to 0.851 with the smaller Yb<sup>3+</sup> cation, the band gap remains statistically unchanged at ~ 1.9&#xa0;eV. This provides the novel insight that, unlike in pure end-member systems, the electronic structure in these half-substituted ferrochromites is predominantly governed by the stable Fe/Cr–O bonding network, making them highly robust against A-site steric deformations. Consequently, these materials demonstrate significant theoretical potential as candidates for future exploratory applications in visible-light photocatalysis and optoelectronics.</p>

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Perovskite distortion mechanisms and optical features unveiled: in-depth study of R(Fe0.5Cr0.5)O3 (R = Tb, Yb) compounds

  • 期刊论文

  • 发表日期：

    2026年4月16日

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  • L. Boudad,
  • A. El Boukili,
  • W. Belayachi,
  • M. Taibi

摘要

Rare-earth-based perovskites R(Fe0.5Cr0.5)O3 (R = Tb, Yb) have been synthesized by the conventional solid-state reaction method to investigate the influence of the A-site cation size on their structural and optical properties. Rietveld refinement of X-ray diffraction (XRD) data confirmed the formation of a single orthorhombic distorted perovskite phase for both materials. The structural distortion evaluated via different parameters has been correlated with the size variation of the rare-earth elements. An in-depth study of the distortion mechanisms has been conducted through Rietveld analysis. Microstructural evaluations using scanning and transmission electron microscopy (SEM/TEM), alongside Scherrer’s equation and Williamson-Hall analysis, confirmed their highly polycrystalline nature. The evidence of stoichiometry and the homogeneous, random distribution of elements within the compounds was highlighted through energy-dispersive X-ray spectroscopy (EDX) and elemental mapping. Vibrational studies (FTIR and Raman spectroscopy) further supported the structural findings, demonstrating that while overall spectral symmetries remain consistent, the Cr/FeO6 octahedral tilt angles and bond lengths shift in response to the A-site cation size. Optical property analysis reveals direct band gap energies of 1.90(6) eV for Tb(Fe0.5Cr0.5)O3 and 1.93(4) eV for Yb(Fe0.5Cr0.5)O3. Notably, while the tolerance factor decreases from 0.869 to 0.851 with the smaller Yb3+ cation, the band gap remains statistically unchanged at ~ 1.9 eV. This provides the novel insight that, unlike in pure end-member systems, the electronic structure in these half-substituted ferrochromites is predominantly governed by the stable Fe/Cr–O bonding network, making them highly robust against A-site steric deformations. Consequently, these materials demonstrate significant theoretical potential as candidates for future exploratory applications in visible-light photocatalysis and optoelectronics.