Introducing Ta2O5 nanoparticles into Ca3Co4O9 matrix for increased thermoelectric property through phonon scattering.

Ta 2 O 5 nanoparticles were synthesized by thermal decomposition of tantalum (V) ethoxide, and Ca 3 Co 4 O 9 /Ta 2 O 5 composites were fabricated by ball milling. The volume percentage of Ta 2 O 5 nanoparticles in the composites was controlled as 0, 2%, 4%, and 6% in four samples. The existence and dispersion of Ta 2 O 5 nanoparticles in the composites were confirmed by electron microscopies. The Ca 3 Co 4 O 9 /Ta 2 O 5 composite particles were hot-pressed into pellets and sintered for thermoelectric property measurement. The impacts of the Ta 2 O 5 volume percentage on the lattice/electronic thermal conductivity, Seebeck coefficient, electrical conductivity, and thermoelectric Figure of Merit (ZT) of the Ca 3 Co 4 O 9 /Ta 2 O 5 composites were investigated. The results indicated that an increased Ta 2 O 5 volume percentage resulted in decreased electrical conductivity and thermal conductivity. When the Ta 2 O 5 was 4 vol %, the highest Seebeck coefficient, and maximum ZT were observed in the Ca 3 Co 4 O 9 /Ta 2 O 5 composite. [ABSTRACT FROM AUTHOR]