2024-03-28T16:50:52Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/803792022-11-17T02:08:08Zhdl_2115_20057hdl_2115_148Anisotropic Heat Conduction in IonāSubstituted Layered Cobalt OxidesCho, Hai JunTakashima, YugoNezu, YukioOnozato, TakakiOhta, Hiromichianisotropyepitaxial filmslayered cobalt oxidesthermal conductivitythermoelectric properties430Layered cobalt oxides, A(x)CoO(2) (A = Li, Na, Ca, and Sr), are attracting attention as thermoelectric materials showing large thermoelectric figure of merit ZT = S-2 sigma T kappa(-1) (S: thermopower, sigma: electrical conductivity, T: absolute temperature, kappa: thermal conductivity) at higher temperatures. Due to the layered structure, A(x)CoO(2) shows strong anisotropy in the thermoelectric properties; both S and sigma are large along the layer though systematic study in kappa is not reported thus far. Here, the anisotropy in kappa of A(x)CoO(2) is shown systematically with the effect of A(x) on kappa. A(x)CoO(2) epitaxial films are fabricated with two different crystallographic orientations with respect to the surface normal to the substrates and the kappa is measured in normal to the substrate. The kappa parallel to the layers (kappa(||)) is 3-6 times larger than that perpendicular to the layers (kappa(perpendicular to)). The kappa(||) decreases with increasing the atomic mass of A(x) though kappa(perpendicular to) is insensitive to it; anisotropy of kappa is controlled by substituting heavier A(x) ions. The present result provides new material design concept for good thermoelectric materials.John Wiley & SonsJournal Articleapplication/pdfhttp://hdl.handle.net/2115/80379https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/80379/1/%28Final%29%20Manuscript_Anisotropic%20heat%20conduction%20of%20AxCoO2.pdf2196-7350Advanced Materials Interfaces7319018162020-02-07enginfo:doi/10.1002/admi.201901816This is the peer reviewed version of the following article: Cho, H. J., Takashima, Y., Nezu, Y., Onozato, T., Ohta, H., Anisotropic Heat Conduction in IonāSubstituted Layered Cobalt Oxides. Adv. Mater. Interfaces 2020, 7, 1901816, which has been published in final form at https://doi.org/10.1002/admi.201901816 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.author