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<p>In this work, CaMnO<sub>3</sub> was co-doped with lanthanum (La<sup>3</sup>⁺) at the A-site and niobium (Nb<sup>5</sup>⁺) at the B-site to systematically investigate the influence of co-doping on its thermoelectric properties. The samples were synthesized using a cost-effective solid-state reaction method. Rietveld-refined XRD analysis confirm the phase-pure orthorhombic structure of the synthesized ceramics of both pure and La/Nb co-doped CaMnO<sub>3</sub>. FE-SEM analyses reveal that La–Nb co-doping in CaMnO<sub>3</sub> effectively refines grains, enhances densification, and ensures uniform elemental distribution, leading to improved microstructural control. EDS analysis shows the elements peak of the La, Nb, Ca, Mn, and O. FTIR spectra of CaMnO<sub>3</sub> and La/Nb co-doped CaMnO<sub>3</sub> revealed characteristic Mn–O vibrations. The observed doping-induced shifts in the metal–oxygen bond regions highlighted lattice distortion and successful dopant incorporation. Electrical conductivity measurements showed that co-doping led to a significant enhancement in conductivity, which was attributed to the increased carrier concentration and improved Mn<sup>3</sup>⁺/Mn<sup>4</sup>⁺ hopping pathways. A maximum electrical conductivity of 253 S·cm⁻<sup>1</sup> at 580&#xa0;K was obtained for Ca<sub>0</sub>.<sub>90</sub>La<sub>0</sub>.<sub>10</sub>Mn<sub>0</sub>.<sub>90</sub>Nb<sub>0</sub>.<sub>10</sub>O<sub>3</sub>, which is approximately two orders of magnitude higher than that of undoped CaMnO<sub>3</sub>. The negative Seebeck coefficient values confirm n-type behavior, and the values decrease at higher doping levels. Notably, the power factor substantially increased, reaching a maximum value of 289&#xa0;µW·m⁻<sup>1</sup>·K⁻<sup>2</sup> at 1074&#xa0;K for 0.025 La/Nb co-doped CaMnO<sub>3</sub>.</p>

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La3⁺ and Nb5⁺ co-doped CaMnO3 ceramics for thermoelectric applications

  • 期刊论文

  • 发表日期：

    2025年10月17日

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  • M. Govardhan,
  • B. Kasiviswanathan,
  • R. Dhanaraj,
  • A. Sulthan Ibrahim,
  • K. Mohanraj,
  • G. Sivakumar

摘要

In this work, CaMnO3 was co-doped with lanthanum (La3⁺) at the A-site and niobium (Nb5⁺) at the B-site to systematically investigate the influence of co-doping on its thermoelectric properties. The samples were synthesized using a cost-effective solid-state reaction method. Rietveld-refined XRD analysis confirm the phase-pure orthorhombic structure of the synthesized ceramics of both pure and La/Nb co-doped CaMnO3. FE-SEM analyses reveal that La–Nb co-doping in CaMnO3 effectively refines grains, enhances densification, and ensures uniform elemental distribution, leading to improved microstructural control. EDS analysis shows the elements peak of the La, Nb, Ca, Mn, and O. FTIR spectra of CaMnO3 and La/Nb co-doped CaMnO3 revealed characteristic Mn–O vibrations. The observed doping-induced shifts in the metal–oxygen bond regions highlighted lattice distortion and successful dopant incorporation. Electrical conductivity measurements showed that co-doping led to a significant enhancement in conductivity, which was attributed to the increased carrier concentration and improved Mn3⁺/Mn4⁺ hopping pathways. A maximum electrical conductivity of 253 S·cm⁻1 at 580 K was obtained for Ca0.90La0.10Mn0.90Nb0.10O3, which is approximately two orders of magnitude higher than that of undoped CaMnO3. The negative Seebeck coefficient values confirm n-type behavior, and the values decrease at higher doping levels. Notably, the power factor substantially increased, reaching a maximum value of 289 µW·m⁻1·K⁻2 at 1074 K for 0.025 La/Nb co-doped CaMnO3.