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<p>This study examines the impact of substituting copper with monovalent cations (Li<sup>+</sup>, Na<sup>+</sup>, and K<sup>+</sup>) in Bi<sub>4</sub>V<sub>1.8</sub>Cu<sub>0.2</sub>O<sub>10.7</sub> on its structural, optical, and microstructural properties. The Bi<sub>4</sub>V<sub>1.8</sub>Cu<sub>0.2−<i>x</i></sub>M<sub><i>x</i></sub>O<sub>10.7−<i>x</i>/2</sub> (M = Li<sup>+</sup>, Na<sup>+</sup>, K<sup>+</sup>) solid solutions were synthesized using the solid-state route. XRD and Raman confirmed the stabilization of the tetragonal <i>γ</i>-phase across all samples. SEM revealed sodium substitution promoted grain growth and densification, while lithium substitution generated heterogeneous microstructures with microcracks. FT-IR spectra showed shifts in vibrational bands, evidencing the effect of cation size on Bi–O and V–O bonding. (DRS) showed that monovalent substitution effectively tunes the optical bandgap: Li-substituted samples exhibit <i>E</i><sub>g</sub> = 2.02–2.18&#xa0;eV, Na-substituted samples 2.13–2.19&#xa0;eV, and K-substitution (<i>x</i> = 0.05) 2.03&#xa0;eV, all lower than Bi<sub>4</sub>V<sub>2</sub>O<sub>11</sub> (2.86&#xa0;eV). The smallest <i>E</i><sub>g</sub> values occur for Bi<sub>4</sub>V<sub>1.8</sub>Cu<sub>0.15</sub>Li<sub>0.05</sub>O<sub>10.675</sub> and Bi<sub>4</sub>V<sub>1.8</sub>Cu<sub>0.15</sub>K<sub>0.05</sub>O<sub>10.675</sub>. These results demonstrate that monovalent cation substitution efficiently tunes the optical response of Bi<sub>4</sub>V<sub>2</sub>O<sub>11</sub>-based materials for practical applications.</p> Graphical abstract <p></p>

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Structural, microstructural, and optical modifications induced by monovalent cation substitution in Bi4V1.8Cu0.2O10.7 (M = Li+, Na+, and K+)

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • W. Mhaira,
  • A. Agnaou,
  • R. Essalim,
  • M. Zamama,
  • A. Ammar

摘要

This study examines the impact of substituting copper with monovalent cations (Li+, Na+, and K+) in Bi4V1.8Cu0.2O10.7 on its structural, optical, and microstructural properties. The Bi4V1.8Cu0.2−xMxO10.7−x/2 (M = Li+, Na+, K+) solid solutions were synthesized using the solid-state route. XRD and Raman confirmed the stabilization of the tetragonal γ-phase across all samples. SEM revealed sodium substitution promoted grain growth and densification, while lithium substitution generated heterogeneous microstructures with microcracks. FT-IR spectra showed shifts in vibrational bands, evidencing the effect of cation size on Bi–O and V–O bonding. (DRS) showed that monovalent substitution effectively tunes the optical bandgap: Li-substituted samples exhibit Eg = 2.02–2.18 eV, Na-substituted samples 2.13–2.19 eV, and K-substitution (x = 0.05) 2.03 eV, all lower than Bi4V2O11 (2.86 eV). The smallest Eg values occur for Bi4V1.8Cu0.15Li0.05O10.675 and Bi4V1.8Cu0.15K0.05O10.675. These results demonstrate that monovalent cation substitution efficiently tunes the optical response of Bi4V2O11-based materials for practical applications.

Graphical abstract