Thermoelectric properties of oxides Ca/sub 2/Co/sub 2/O/sub 5/ with Cr substitution

Abstract

In recent years, oxide ceramics, such as NaCoO, Ca/sub 2/Co/sub 2/O/sub 5/ have attracted significant research interest for their prominent thermoelectric properties. In this paper, we investigated the high temperature thermoelectric properties of Ca/sub 2/Co/sub 2/O/sub 5/ with Cr substitution. CaCO/sub 3/,Co/sub 3/O/sub 4/ and Cr/sub 2/O/sub 3/ powders were used as the starting mixture. These powders were mixed by ball milling and sintered by a pulsed electric current sintering method (PECS) in Ar gas atmosphere. Both the electrical conductivity and Seebeck coefficient of the sintered bodies were simultaneously measured in He gas atmosphere from room temperature up to 1000 K. The electrical conductivity of Ca/sub 2-x/Cr/sub x/Co/sub 2/O/sub 5/ increased with increasing Cr content and reached a peak at x=0.3. The Seebeck coefficients of all the sintered bodies are positive, indicating p-type materials. The power factor of Ca/sub 2-x/Cr/sub x/Co/sub 2/O/sub 5/ increased with increasing Cr content, and the sample with x=0.3 showed the highest power factor 2.9 /spl times/ 10/sup -4/ W/mK/sup 2/ at 800/spl deg/C.