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<p>In this work, we report the influence of Cobalt incorporation with varying concentrations (0–5%) on the crystalline phase, morphology, and optical and dielectric properties of BaTiO<sub>3</sub> synthesized through a sol–gel process. The structural and morphological properties were investigated by XRD, FTIR, FE-SEM, XPS, and TEM. XRD analysis indicated a cubic perovskite structure with progressive development of tetragonal character upon cobalt doping, evidenced by systematic peak splitting at ~ 45° and 65°, with apparent c/a ratios reaching 1.026 at 5% Co, and systematic suppression of a BaCO<sub>3</sub> impurity phase from 29.17% relative intensity in C0 to almost complete elimination at 5% Co. FTIR examination confirmed the perovskite structure and highlighted consistent changes in metal–oxygen bonding as the cobalt concentration rose. TEM analysis reveals roughly spherical nanoparticles with mean particle sizes of 26.0&#xa0;nm and 19.4&#xa0;nm for C0 (0% Co) and C3 respectively, consistent with XRD Scherrer crystallite sizes, with C3 (5% Co) showing increased agglomeration and morphological irregularity compared to C0. XPS of representative samples C0 and C3 revealed Co<sup>2+</sup>/Co<sup>3+</sup> B-site substitution, mixed Ti<sup>3+</sup>/Ti<sup>4+</sup> states, and a significant O1s shift of 1.35&#xa0;eV, confirming oxygen vacancy formation as the central charge compensation mechanism. The optical energy band gap was calculated from diffuse reflectance measurements and found to decrease from 3.39 to 3.00&#xa0;eV with Co-doping. Dielectric analysis revealed a four-stage concentration-dependent evolution: C0 and C1 show nanosize-suppressed response, C2 shows thermally activated defect contributions, and C3 shows dramatic permittivity enhancement up to ~ 800 driven by three concurrent mechanisms: Co<sup>2+</sup>/Co<sup>3+</sup> hopping conduction, Ti<sup>3+</sup>-oxygen vacancy defect dipole relaxation, and domain wall motion from tetragonal domains, suggesting potential suitability for capacitor and temperature-responsive device applications in lead-free, energy-efficient electronics, pending further device-level evaluation.</p>

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Structural, optical, and dielectric properties of cobalt substituted barium titanate nanoparticles for advanced electronic applications

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Hisham A. Saleh,
  • Abdullah Alsulami

摘要

In this work, we report the influence of Cobalt incorporation with varying concentrations (0–5%) on the crystalline phase, morphology, and optical and dielectric properties of BaTiO3 synthesized through a sol–gel process. The structural and morphological properties were investigated by XRD, FTIR, FE-SEM, XPS, and TEM. XRD analysis indicated a cubic perovskite structure with progressive development of tetragonal character upon cobalt doping, evidenced by systematic peak splitting at ~ 45° and 65°, with apparent c/a ratios reaching 1.026 at 5% Co, and systematic suppression of a BaCO3 impurity phase from 29.17% relative intensity in C0 to almost complete elimination at 5% Co. FTIR examination confirmed the perovskite structure and highlighted consistent changes in metal–oxygen bonding as the cobalt concentration rose. TEM analysis reveals roughly spherical nanoparticles with mean particle sizes of 26.0 nm and 19.4 nm for C0 (0% Co) and C3 respectively, consistent with XRD Scherrer crystallite sizes, with C3 (5% Co) showing increased agglomeration and morphological irregularity compared to C0. XPS of representative samples C0 and C3 revealed Co2+/Co3+ B-site substitution, mixed Ti3+/Ti4+ states, and a significant O1s shift of 1.35 eV, confirming oxygen vacancy formation as the central charge compensation mechanism. The optical energy band gap was calculated from diffuse reflectance measurements and found to decrease from 3.39 to 3.00 eV with Co-doping. Dielectric analysis revealed a four-stage concentration-dependent evolution: C0 and C1 show nanosize-suppressed response, C2 shows thermally activated defect contributions, and C3 shows dramatic permittivity enhancement up to ~ 800 driven by three concurrent mechanisms: Co2+/Co3+ hopping conduction, Ti3+-oxygen vacancy defect dipole relaxation, and domain wall motion from tetragonal domains, suggesting potential suitability for capacitor and temperature-responsive device applications in lead-free, energy-efficient electronics, pending further device-level evaluation.