Synthesis and Characterization of Ca₃Co₄O₉ Thermoelectric Ceramics using the Slurry Sintering Method

Abstract

Ca₃Co₄O₉ samples were made by the sintering method using the slurry consisted of Ca₃Co₄O₉ powder and Ca₃Co₄(OH)₁₈ hydroxide in binder solution. The preparation conditions for making the crack free samples were examined, and we found that using the slurry having a mixing ratio of Ca₃Co₄O₉ powder to 13 wt.% or 18 wt.% Ca₃Co₄(OH)₁₈ hydroxide in binder solution of 10:1.5, samples with a few crack could be prepared. From SEM observation, it was found that the void density in Ca₃Co₄O₉ samples could be controlled by the slurry sintering method. The electric conductivity (σ), Seebeck coefficient (S), and power factor (PF) of samples prepared by slurry sintering method at room temperature are 53 S/cm, 118 µV/K and 73.8 µWm^-1K^-2, respectively. The power factor (PF) at 600 °C was 173 µWm^-1K^-2.