An investigation of thermoelectric properties of Sb and B doped Ca3Co4O9 oxide compound

In this thesis, both thermoelectric and magnetic properties of Ca3Co4O9 compound fabricated by solid state reaction technique were investigated. The effects of Sb and B substitution for Ca on Ca3Co4O9 on ZT coefficient were examined. Materials fabricated was characterized by micro-structural, magnetic and thermoelectric properties.The Sb substitutions caused to decrease the thermoelectric performance of samples, however, the B substitution showed different thermoelectric behavior depending on substitution level. The thermoelectric performance for x=0.5 B substitution increased. The ZT coefficient was obtained 3.5 times higher than un-substituted sample. It is found that ZT coefficient room temperature was 25x10-4 for this compound. The samples showed a paramagnetic-ferrimagnetic phase transition at low temperatures depending on substitution level and elements.Keywords: Thermoelectricity, Oxide Thermoelectric material, Ca3Co4O9.