NDLI: Thermoelectric properties and local electronic structure of rare earth-doped Ca3Co2O6

Content Provider	IEEE Xplore Digital Library
Author	Nong, N.V. Ohtaki, M.
Copyright Year	2006
Description	Author affiliation: Interdisciplinary Graduate Sch. of Eng. Sci., Kyushu Univ., Fukuoka (Nong, N.V.; Ohtaki, M.)
Abstract	Thermoelectric properties of a series of rare earth metal-doped polycrystalline samples of $(Ca_{1-x}R_{x})_{3}Co$ $_{2}O_{6}$ with R = Gd, Tb, Dy and Ho (x = 0 - 0.1) were investigated in the temperature range from 300 K to 1300 K. In a high temperature region above 900 K, a partial rare earth substitution with R $^{3+}$ for $Ca^{2+}$ resulted in appreciable increase in the Seebeck coefficient (S). However, the S value decreased abruptly at low temperatures, and turned to negative values for the Gd- and Tb-doped samples at temperatures below 400 K. With decreasing ionic radii of rare earth elements $(Gd^{3+}$ > $Tb^{3+}$ > $Dy^{3+}$ > $Ho^{3+}),$ the S values increased, while the thermal conductivity (kappa) decreased particularly at temperatures above 700 K. Contrastingly, the influence of rare earth metal substitution on the electrical resistivity (rho) was small; in high temperature region the rho values increased only slightly with decreasing ionic radii of rare earth metals. High-temperature thermoelectric figure-of-merit (Z) of the samples was thereby improved by the late rare-earth metal substitution for $Ca^{2+},$ particularly for those with $Ho^{3+}.$ A maximum Z value of the Ho-doped sample for x = 0.03 was 1.83 times $10^{-4}$ K-1at 1100 K as compared with 0.37 times $10^{-4}$ K-1for non-doped sample. The electronic structure of the samples was also investigated by x-ray photoemission spectroscopy (XPS) technique. The charge-transfer satellite structure of Co 2p core-level spectra was observed for the Gd-and Tb-doped samples, while the satellite is negligible for the other samples
Starting Page	62
Ending Page	65
File Size	4925500
Page Count	4
File Format	PDF
ISBN	1424408105
ISSN	10942734
DOI	10.1109/ICT.2006.331270
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2006-08-06
Publisher Place	Austria
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Thermoelectricity Thermal conductivity Temperature distribution Powders Geoscience Electric resistance Spectroscopy Satellites Crystalline materials Crystals
Content Type	Text
Resource Type	Article

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