Fabrication and properties of textured Bi-based cobaltite thermoelectric rods by zone melting

The performance of a thermoelectric material can be increased when the electrical conductivity is raised. This could be performed by aligning grains along a preferential direction using, for example, the laser floating zone (LFZ) method. This technique has indeed demonstrated its potentiality to increase the electrical conductivity on various ceramic materials. Moreover, with this technique, it is possible to grow samples at higher rates than with other techniques owing to the large thermal gradients developed at the melt-solid interface. The large grain sizes obtained by LFZ lead to samples with improved properties. This paper reports the synthesis of thermoelectric bars by the LFZ technique. The properties (electrical resistivity (ρ) and thermopower) of directionally solidified Bi-based cobaltite rods are determined and correlated with the structural features (XRD and SEM-EDX).