Highly Oxygen-Deficient Topotactic BaBixCo1−xO3−δ (0 ≤ x ≤ 0.2) Perovskites with Enhanced Oxygen Dynamics for High Temperature Thermoelectric Applications.

Oxygen stoichiometry plays a vital role in determining the physical properties of transition metal oxides (TMOs) and their suitability for high-temperature thermoelectric applications. In the present study, oxygen-deficient BaBi_xCo_1–xO_3–δ (0 ≤ x ≤ 0.2) perovskite samples were synthesized using the sol-gel method. Structural analysis revealed the formation of oxygen-deficient phases with hexagonal structures. Morphological analysis showed significant changes in the size and interlayer growth of these phases with various levels of bismuth (Bi) substitution. The high thermal stability of the samples was confirmed by TGA. The binding state and composition of the samples were analysed by XPS. Thermoelectric studies were performed, and the results indicated that the electrical resistivity (ρ) decreased with temperature, indicating the semiconducting behavior of the samples. The Seebeck coefficient (S) increased for the samples with higher Bi content due to energy filtering effect. The sample with x value of 0.1 shows a high-power factor of 0.001 µWK^{− 2}m^{– 1} at 600 K compared to other samples. The experimental findings demonstrated that the oxygen deficient BaBi_xCo_1–xO_{3 – δ} perovskite material exhibited high thermoelectric performance compared to the sample with mixed phase. Furthermore, Bi substitution was found to be a promising strategy for enhancing the thermoelectric performance, with specific compositions showing great potential for high-temperature thermoelectric applications. [ABSTRACT FROM AUTHOR]