Tuning Ca3Co4O9 thermal and transport properties by TiC nanoparticles addition

Calcium cobaltite, a promising oxide for energy harvesting: effective strategies toward enhanced thermoelectric performance

“…Recently, it was shown that dispersions of nano-sized inclusions of additives, such as ln 2 O 3 , Ta 2 O 5 , and TiC [94][95][96], into the calcium cobaltite matrix is an efficient way to reduce thermal conductivity. As these nano-sized additives do not react with the matrix phase, they become embedded in the grain boundaries and interfaces, and act as scattering centers, reducing the mean free path of phonons via Rayleigh-type and geometrical phonon scattering mechanisms (figure 6) [97].…”

“…As these nano-sized additives do not react with the matrix phase, they become embedded in the grain boundaries and interfaces, and act as scattering centers, reducing the mean free path of phonons via Rayleigh-type and geometrical phonon scattering mechanisms (figure 6) [97]. For example, calcium cobaltite ceramics containing 4.0 vol.% nanoparticles of Ta 2 O 5 (about 9.25 nm in size) or 0.25 wt.% TiC (< 200 nm in size) showed about 30% reduction in thermal conductivity at 372 K, compared to the pristine calcium cobaltite [95,96]. Conversely, Ag particles (<1000 nm in size) are frequently used to increase electrical conductivity, as the highly conductive Ag is able to create new carrier transport routes inside the composite [98,99].…”