Low temperature thermopower and electrical transport in misfit Ca₃Co₄O₉with elongatedc-axis

Abstract

The temperature dependence of the electrical resistivity (ρ) and thermopower (S) of misfit cobaltite Ca3Co4O9 has been studied. The compound is a promising thermoelectric material, exhibiting very low ρ(∼1.3 × 10−4 Ω cm) and reasonably high S (∼56 µV K−1) at room temperature, which is desirable for thermoelectric applications. At T < 80 K, S exhibits T3/2 dependence, suggesting that electron–magnon scattering has a pronounced influence on S at low temperatures. Ca3Co4O9 exhibits a temperature independent power factor in the temperature range 300–80 K. A comparison of the temperature dependence of the power factor of Ca3Co4O9 with various materials projected or used as a thermoelectric cooler (e.g. single crystal of short c-axis Ca3Co4O9, polycrystalline La0.95Sr0.05CoO3, Bi0.85 Sb0.15, Bi2Te3, Bi-SiO2 composite) indicates that title compound Ca3Co4O9 is a much superior candidate for thermoelectric applications.

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

“…In the case of Ca 3 Co 4 O 9 ceramic materials, it is essential to find an additive compatible with this phase, with a melting point close to the sintering temperature, and which is not reacting with any one of the matrix components. In the literature, many examples of these kind of materials can be found as part of the fluxes used to grow Ca 3 Co 4 O 9 single crystals [13,14]. Among these materials, K 2 CO 3 possess melting point (899 ºC) [15] very close to the optimal Ca 3 Co 4 O 9 materials sintering temperature, as reported in previous works [16].…”

Effect of grain size and porosity on phonon scattering enhancement of Ca3Co4O9

“…This compound belongs to the family of misfit cobalt oxides, and the structure of the crystal can be described as an alternate stacking along [0 0 1] of distorted rock-salt-type slabs [Ca 2 CoO 3 ] and [CoO 2 ] layers, resulting in a distorted CdI 2 -type structure [34]. In these layers, the CoO 2 nanosheets contain a strongly correlated electron system and a Ca 2 CoO 3 misfit layer, which serves as an electronic transport layer acting as a potential phonon scattering region [35][36][37][38].…”

High temperature thermoelectric properties and energy transfer devices of Ca3Co4−xAgxO9 and Ca1−ySmyMnO3

“…Therefore, considerable efforts have been dedicated to the investigation of TE materials in the past decades. In comparison to conventional TE materials, such as Bi 2 Te 3 [7][8][9][10][11][12] and PbTe [13][14][15] based alloys, high-temperature oxide TE materials, including Ca 3 Co 4 O 9 [16][17][18][19][20], NaCoO 2 [21][22][23][24], Li-doped NiO [25], CaMnO 3 [26][27][28][29], and SrTiO 3 [30], are of particular interest to researchers as a result of their high TE performance, nontoxic nature and high thermal and chemical stability.…”