Improvement of the thermoelectric properties of [Bi1.68Ca2O4−δ][CoO2]1.69 cobaltite by chimie douce methods

Bi_1.68Ca₂O_4−δ]^RSCoO₂]_1.69 has been obtained by different chimie douce methods and uniaxially or isostatically pressed. The influence of these parameters on the thermoelectric properties has been investigated. Contrary to the Seebeck coefficient, which remains unchanged, the electrical conductivity is greatly modified. In particular, spray-drying synthesis followed by uniaxial pressing results in an electrical conductivity two times larger than in the case of conventional solid state synthesis. Our results suggest that a narrow particle size distribution is beneficial to the thermoelectric properties of the layered compounds. The spray-drying technique seems to be promising to improve the electrical conductivity of layered materials. Moreover, this method presents other advantages (homogeneous samples and less energetic processing) which could be interesting to the future manufacturing of thermoelectric devices.