| Abstract Scope |
Sodium cobaltite NaxCoO2 is a highly promising p-type cobalt oxide material for thermoelectric applications. However, its susceptibility to thermal degradation in air limits its use in high-temperature environments such as industrial waste heat recovery. To overcome this challenge, we embedded larger-sized NaxCoO2 template particles within a thermally stable Ca3Co4-yO9+δ-NaxCoO2-Bi2Ca2Co2O9 triple-phase matrix, aiming to enhance texture and thermoelectric performance. The fabrication involved cold-pressing and pressureless sintering in air. Hexagonal NaxCoO2 template particles, synthesized via molten-flux, ensured precise control over size and shape, while the matrix was produced via sol-gel synthesis. The resulting textured composite, with 20 % template particle content, exhibited enhanced thermal stability, resisting decomposition at 1173 K compared to template particles, which decompose at 1073 K. Enhanced electrical transport properties were observed, improving thermoelectric performance due to increased Seebeck coefficient from template-matrix lattice mismatch and improved electrical conductivity from texturization, verified by X-ray diffraction and scanning electron microscopy. |