Low-Temperature Thermoelectric Properties of the Composite Crystal [Ca ₂CoO _3.34] _0.614[CoO ₂]

Abstract

Electric resistivity, thermoelectric power and thermal conductivity of a polycrystalline sample of the composite crystal [Ca2CoO3.34]0.614[CoO2], also known as Ca3Co4O9, have been measured below 300 K. Metallic conductivity accompanied by large thermoelectric power has been observed down to 50 K. At 300 K, the sample exhibits a thermoelectric power of S = 133 µV·K-1, resistivity of ρ= 15 mΩ·cm and thermal conductivity of κ= 9.8 mW·K-1·cm-1. The resulting dimensionless figure of merit becomes Z T 300 = 3.5×10-2, which is comparable to the value reported for a polycrystalline sample of NaCo2O4, indicating that the title compound is a potential candidate for a thermoelectric material.

Fabrication and thermoelectric characteristics of [(Bi,Pb)2Ba2O4±w]0.5CoO2 bulks with highly aligned grain structure

“…1 In recent years, "misfit-layered cobalt oxides" have been highlighted as next-generational TE materials. [2][3][4][5][6] The members of this material family possess a crystal structure consisting of alternate stacks of a hexagonal CoO 2 layer ͑of the CdI 2 structure͒ and a multi-square-plane layer, M m A 2 O 2+mϮ ͓of the rock-salt ͑RS͒ structure͔. The general chemical formula may be given by ͓M m A 2 O 2+mϮ ͔ q CoO 2 ͑M = Bi, Pb, Co, etc., A = Ba, Sr, etc., m =0, 1, or 2͒, where q is the ratio of b-axis lengths of the two layers, i.e., q ϵ b CoO 2 / b RS .…”

Microstructures and Thermoelectric Properties of Sintered Ca3Co4O9-Based Oxide

“…The indices in the diffraction pattern and the incident direction were defined by the four-dimensional superspace group approach (2) . From the comparison of Fig.…”

“…3 (b), b CoO2 is nearly constant as y changes, whereas b RS decreases with increasing y. These results suggest that Zn and Ti substitute in the rocksalt layer rather than in the CoO 2 The density of the sintered pellet for x = y = 0 was measured to be 3.98 g/cm layer.…”

High Pressure Sintering of Nano-polycrystalline Thermoelectric Materials

“…[1] [2 5] Co [6,7] [8] In this article we describe the possibility of the improvement of thermoelectric properties of polycrystalline materials through means of high pressure sintering. We made an attempt to reduce the thermal conductivity, which is one of the important parameter of thermoelectric properties, by the high pressure sintering of nano-crystalline particles.…”