Thermoelectric performance of Bi- and Na-substituted Ca3Co4O9 improved through ceramic texturing

Abstract

Plate-like particles of Ca 3 Co 4 O 9 have been prepared in which Bi and Na were partially substituted for Ca to improve the thermoelectric performance. Successfully fabricated dense and highly textured ceramics have been obtained by combining the templated grain growth technique (TGG) with hot-pressing (HP). Ca 3 Co 4 O 9 single crystals, which have alternating layers of Co-O and Ca-Co-O in the direction of the c-axis, show high electrical conductivity along the layer compared with that across the layer. Hence, a highly oriented TGG 1 HP specimen showed high electrical conductivity compared with the specimen sintered under uniaxial pressure (UP 1 PLS). The improved electrical conductivity with high Seebeck coefficient of the highly oriented specimen (TGG 1 HP) gave a high thermoelectric power factor of 5.9 6 10 24 W m 21 K 22 at 1073 K. The figures-of-merit at 773 K and 1073 K were calculated to be 8.54 6 10 25 K 21 (ZT ~0.066 at 773 K) and 1.69 6 10 24 K 21 (ZT ~0.18 at 1073 K), respectively. These values are quite high among Ca-Co-O polycrystalline systems reported so far.

Thermoelectric Ca3Co4O9 ceramics consolidated by Spark Plasma sintering

“…Single crystal composite templating [18], reactive template grain growth [19], hot pressing [20], sinter-forging [11,21], and magnetic field [22] are also used to densify and/or to induce an orientation between grains. In addition, the novel Spark Plasma Sintering (SPS) technique has been developed and commonly used nowadays to prepare various materials [23][24][25][26][27].…”

Formation of Lithium‐Driven Active/Inactive Nanocomposite Electrodes Based on Ca3Co4O9 Nanoplates

“…This compound, which has a misfit structure consisting of a single CdI 2 -type [CoO 2 ] layer stacked with [CoCa 2 O 3 ] rock-salt-type layers with different in-plane lattice parameters b, has been reported to have high thermoelectric properties. [14][15][16] Herein, we report the first application of a thermoelectric material, namely, Ca 3 Co 4 O 9 nanoplates with high electrical conductivity, to a Li-ion-battery anode. Furthermore, the formation of lithium-active/inactive nanocomposites during the charge/discharge process is carefully investigated.…”

Design of Grain Oriented Microstructure by the Monte Carlo Simulation of Sintering and Isotropic Grain Growth

“…The strategy of this method evolved into the templated grain growth (TGG) method. The TGG method was developed to fabricate highly tex tured ceramics: e.g., Si 3 N 4 , 5) 15) and Na x CoO d . 16), 17) In this method, a small amount of template particles with an anisotropic (e.g., platelike or needlelike) shape are used as the seed materials for the grain growth.…”