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<p>A comprehensive study on R<sub>0.7</sub>Sr<sub>0.3</sub>CoO<sub>3</sub> (R = La, Pr, Nd) perovskite cobaltites was conducted to investigate the influence of the A-site ionic radius on their structural, magnetic, electrical, and thermoelectric properties. XRD analysis confirmed a phase transition from rhombohedral (La) to orthorhombic (Pr, Nd) structures with decreasing R<sup>3+</sup> radius. Scanning electron microscopy (SEM) revealed a reduction in grain size (~ 5&#xa0;μm) and porosity with decreasing R³⁺ ionic radius, indicating enhanced grain boundary scattering and degradation in electrical conductivity and mechanical integrity. Electrical resistivity exhibited semiconducting behavior governed by small polaron hopping and variable-range hopping mechanisms, increasing resistivity and activation energy across the series. Magnetization measurements revealed a paramagnetic to ferromagnetic transition, with a Curie temperature that decreased from 224&#xa0;K to 145&#xa0;K, which was linked to weakened Co<sup>3+</sup>-O-Co<sup>4+</sup> interactions and increased structural distortion. Thermopower results indicated p-type conduction, with Seebeck coefficients increasing as R<sup>3+</sup> ionic size decreased and sign reversals suggesting multiband transport. These findings underline the critical role of A-site engineering in tuning the multifunctional behavior of cobaltites.</p>

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Evolution of structural, magnetic, electrical, and thermal studies of R0.7Sr0.3CoO3 (R = La, Pr, Nd) cobaltites

  • 期刊论文

  • 发表日期：

    2025年11月10日

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  • Prachi Joshi,
  • Anchit Modi,
  • Shivani K. Kapoor,
  • Ashutosh Mishra

摘要

A comprehensive study on R0.7Sr0.3CoO3 (R = La, Pr, Nd) perovskite cobaltites was conducted to investigate the influence of the A-site ionic radius on their structural, magnetic, electrical, and thermoelectric properties. XRD analysis confirmed a phase transition from rhombohedral (La) to orthorhombic (Pr, Nd) structures with decreasing R3+ radius. Scanning electron microscopy (SEM) revealed a reduction in grain size (~ 5 μm) and porosity with decreasing R³⁺ ionic radius, indicating enhanced grain boundary scattering and degradation in electrical conductivity and mechanical integrity. Electrical resistivity exhibited semiconducting behavior governed by small polaron hopping and variable-range hopping mechanisms, increasing resistivity and activation energy across the series. Magnetization measurements revealed a paramagnetic to ferromagnetic transition, with a Curie temperature that decreased from 224 K to 145 K, which was linked to weakened Co3+-O-Co4+ interactions and increased structural distortion. Thermopower results indicated p-type conduction, with Seebeck coefficients increasing as R3+ ionic size decreased and sign reversals suggesting multiband transport. These findings underline the critical role of A-site engineering in tuning the multifunctional behavior of cobaltites.