The phase structure and electrical performance of the limited solid solution CuFeO₂–CuAlO₂ thermoelectric ceramics

The limited solid solutions of nominal (1 − x) CuFeO₂ − xCuAlO₂ have been prepared by conventional solid-state reaction, and thermoelectric property has been measured. From the XRD powder pattern, we found that the major phase of the limited solid solution is rhombohedral delafossite structure when the composition is near the end members. Cubic Cu(Fe,Al)₂O₄ phase has been formed in composition from x = 0.4 to 0.8. Electrical resistivity of samples with major delafossite structure is lower than that of samples with Cu(Fe,Al)₂O₄ phase. In the zone of phase transform, the electrical resistivity can be got with lower value, such as x = 0.2, 0.3 and 0.9. The Seebeck coefficient for the limited solid solution with delafossite structure is positive in whole measured temperature range from 300 to 923 K. In the end, the power factor for the limited solid solution with major delafossite structure shows higher value, which is resulted from the lower electrical resistivity by the phase transposition. The highest power factor of 1.14 × 10⁻⁴ W/mK² has been addressed at 907 K for x = 0.2, which value is enhanced by 3–4 times than that of pure phase CuFeO₂ or CuAlO₂.