Synthesis and Thermoelectric Properties of Ceramics Based on Bi₂Ca₂Co_1.7O_y Oxide

Abstract—Layered ceramics based on bismuth–calcium cobaltite with varied cobalt oxide contents is synthesized by the solid-phase method, the ceramics phase composition is determined, and the microstructure, thermal expansion, electroconductivity, and thermal electromotive force are investigated. The formation of just one compound, ternary oxide composed of Bi₂Ca₂Co_1.7O_y, is established within the quasi-binary Bi₂Ca₂O₅–CoO_z system. The effect of the cobalt oxide content on the Bi₂Ca₂Co_xO_y ceramics’ microstructure and physicochemical properties is analyzed. The single-phased ceramic sample Bi₂Ca₂Co_1.7O_y demonstrated the highest power factor value among all the investigated samples—26.0 µW/(m K²) at a temperature of 300 K. This sample showed the lowest value of the thermal linear expansion coefficient of 9.72 × 10^–6 K^–1.