High-temperature thermoelectric properties of La and Fe co-doped Ca–Co–O misfit-layered cobaltites consolidated by spark plasma sintering

Doping effect in Ca3Co4−xZnxOy ceramics

“…At higher temperatures, this behaviour changes to a metallic-like (dq/dT [ 0) one where the charge carriers are transported in the valence or conduction band [24]. The lowest measured room temperature resistivity values (*16 mX cm for the 0.01 Znsubstituted samples) are close to the values obtained for Ca 3 Co 4 O 9 samples produced by spark plasma sintering (*13 mX cm) [15]. The obtained resistivity values are more impressive when taking into account that they have been obtained in samples prepared by the solid state method, with low densities, and are compared with the obtained in spark plasma sintering prepared ones, with about 98 % of the theoretical density.…”

“…As a consequence, this effect can be exploited to preferentially align these grains to obtain bulk properties close to those obtained in single crystals. Many different techniques have been explored to produce well aligned grains in bulk materials, as hot uniaxial pressing [14], spark plasma sintering [15], laser floating zone melting (LFZ) [16], electrically assisted laser floating zone [17], etc. The main drawbacks of these methods are due to different factors, as the relatively long treatments, the high costs associated with the processes and/or the strong properties dependence on the growth or the texturing speed [14,15,18,19].…”

Tailoring Ca3Co4O9 microstructure and performances using a transient liquid phase sintering additive

“…As bulk materials, these oxides usually demonstrate quite low thermoelectric performance, which make them no feasible for any practical applications. Envisaging the increment of ZT, many processing and structural engineering routes were attempted, including cationic substitution in solid state sintered materials [4,5], or taking advantage of their crystallographic nature to align the grains into a preferential direction using well-known techniques such as templated grain growth (TGG) [6], hot-pressing [7], spark plasma sintering (SPS) [8], laser floating zone (LFZ) [9], or the recently developed electrically assisted laser floating zone (EALFZ) [10]. These texturing techniques have been reported to produce bulk high density materials with well oriented grains, leading to enhanced electrical conductivity.…”

High thermoelectric performance in Bi2-xPbxBa2Co2Oy promoted by directional growth and annealing

“…This process would allow enhancing ZT to values close to the obtained in single crystals. Many techniques have been used to produce such grain alignment, as hot-pressing [15], spark plasma sintering (SPS) [16], laser floating zone (LFZ) [17], or the electrically assisted laser floating zone [18], which have shown their ability to improve TE performance of bulk materials by the alignment of grains. [20].…”