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<p>This study presents a comprehensive comparative analysis of the effects of divalent cation substitutions on the structural, magnetic, electrical, and dielectric properties of lanthanum orthoferrite (LaFe<sub>1−<i>x</i></sub>B<sub><i>x</i></sub>O<sub>3</sub>) (B = Co<sup>+2</sup>, Ni<sup>+2</sup>, Cu<sup>+2</sup>, or Zn<sup>+2</sup>) perovskites at various substitution levels (<i>x</i> = 0.0, 0.1, 0.2, 0.3, 0.5). All samples were synthesized via a cost-effective and environmentally friendly sucrose sol–gel auto-combustion technique. XRD analysis confirmed the formation of single-phase orthorhombic structures with crystallite size in the range of 43 to 11&#xa0;nm for most compositions, with secondary phases emerging only at higher substitution levels of Cu (<i>x</i> = 0.5) and Zn (<i>x</i> = 0.3, 0.5). The lattice parameters exhibited distinctive behaviors: contraction with Co and Ni substitutions, minimal change with Cu, and expansion with Zn, attributed to ionic radius variations and charge compensation mechanisms through mixed-valence states. Magnetization measurements revealed weak ferromagnetic components, with remanent magnetization (<i>M</i><sub>r</sub>) in the range of 10<sup>–3</sup>&#xa0;emu/g in all samples due to uncompensated surface spins in the predominantly antiferromagnetic materials. Electrical conductivity measurements demonstrated significant enhancement in all substituted samples compared to pure LaFeO<sub>3</sub>, with Ni substitution showing the most dramatic improvement (reaching 0.12&#xa0;S&#xa0;cm<sup>−1</sup> at <i>x</i> = 0.3), followed by Co, Zn, and Cu. The conduction mechanisms varied by dopant type, with transition metals capable of variable oxidation states (Co, Ni, Cu) contributing directly to polaronic conduction, while Zn enhanced conductivity primarily through structural modifications. Dielectric measurements revealed strong temperature and frequency dependence, with all substitutions enhancing the dielectric response through Maxwell–Wagner-type interfacial polarization. This systematic comparative study, which to our knowledge has not been reported before, provides new insights into tailoring perovskite properties through selective divalent cation substitutions synthesized by a sucrose auto-combustion route, offering guidelines for specific technological applications.</p>

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Structural, magnetic, electrical, and dielectric properties of Co-, Ni-, Cu-, and Zn-substituted LaFeO3 perovskite nanoceramics synthesized by a sucrose sol–gel route

  • 期刊论文

  • 发表日期：

    2025年10月16日

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  • M. A. Gabal,
  • D. S. Al-Ooseimy,
  • Y. M. Al Angari,
  • A. Awad,
  • A. A. Al-Juaid,
  • Abdu Saeed

摘要

This study presents a comprehensive comparative analysis of the effects of divalent cation substitutions on the structural, magnetic, electrical, and dielectric properties of lanthanum orthoferrite (LaFe1−xBxO3) (B = Co+2, Ni+2, Cu+2, or Zn+2) perovskites at various substitution levels (x = 0.0, 0.1, 0.2, 0.3, 0.5). All samples were synthesized via a cost-effective and environmentally friendly sucrose sol–gel auto-combustion technique. XRD analysis confirmed the formation of single-phase orthorhombic structures with crystallite size in the range of 43 to 11 nm for most compositions, with secondary phases emerging only at higher substitution levels of Cu (x = 0.5) and Zn (x = 0.3, 0.5). The lattice parameters exhibited distinctive behaviors: contraction with Co and Ni substitutions, minimal change with Cu, and expansion with Zn, attributed to ionic radius variations and charge compensation mechanisms through mixed-valence states. Magnetization measurements revealed weak ferromagnetic components, with remanent magnetization (Mr) in the range of 10–3 emu/g in all samples due to uncompensated surface spins in the predominantly antiferromagnetic materials. Electrical conductivity measurements demonstrated significant enhancement in all substituted samples compared to pure LaFeO3, with Ni substitution showing the most dramatic improvement (reaching 0.12 S cm−1 at x = 0.3), followed by Co, Zn, and Cu. The conduction mechanisms varied by dopant type, with transition metals capable of variable oxidation states (Co, Ni, Cu) contributing directly to polaronic conduction, while Zn enhanced conductivity primarily through structural modifications. Dielectric measurements revealed strong temperature and frequency dependence, with all substitutions enhancing the dielectric response through Maxwell–Wagner-type interfacial polarization. This systematic comparative study, which to our knowledge has not been reported before, provides new insights into tailoring perovskite properties through selective divalent cation substitutions synthesized by a sucrose auto-combustion route, offering guidelines for specific technological applications.