High-temperature electrical transport behaviors of the layered Ca 2 Co 2 O 5 -based ceramics

Textured Bi-substituted Ca 2 Co 2 O 5 ceramics have been prepared using a coprecipitation method combined with spark plasma sintering. The Bi substitution is effective in increasing the grain orientation of the Ca 2 Co 2 O 5 -based ceramics (from 0.46 to 0.85). Electrical conductivity increases obviously with partial substitution of Bi 3 + for Ca 2 + (from 113.9 to 142.4 S/cm at 973 K). The Ca 1.92 Bi 0.08 Co 2 O 5 sample exhibits higher power factor ( 4.4 × 10 − 4 W m − 1 K − 2 ) than that of pure Ca 2 Co 2 O 5 ( 3.2 × 10 − 4 W m − 1 K − 2 ) at 973 K, indicating that the Ca 2 Co 2 O 5 system is another promising p -type material for high-temperature thermoelectric applications.