Effect of Gd-doping on thermoelectric properties of Ca3Co4O9+δ ceramics

• Published in: Journal of materials science Vol. 43; no. 21; pp. 6933 - 6937
• Main Authors: Liu, H. Q., Zhao, X. B., Liu, Fu, Song, Y., Sun, Q., Zhu, T. J., Wang, F. P.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-11-2008; Springer; Springer Nature B.V
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Ceramic powders; Ceramics; Characterization and Evaluation of Materials; Chemical industry and chemicals; Chemistry and Materials Science; Classical Mechanics; Crystallography and Scattering Methods; Defects; Doping; Electrotechnical and electronic ceramics; Exact sciences and technology; Figure of merit; Gadolinium; Hopping conduction; Materials Science; Plasma sintering; Polymer Sciences; Seebeck effect; Solid Mechanics; Spark plasma sintering; Technical ceramics; Transport properties; Spark Plasma Sinter; Dope Sample; Thermoelectric Property; Seebeck Coefficient; Negative Temperature Coefficient; Scanning electron microscopy; Cobalt Oxides; Electrical properties; Property composition relationship; Doping; Temperature effect; Experimental study; Precursor; Oxide ceramics; Powder; Thermoelectric properties; Spark plasma sintering; Transmission electron microscopy; Impurity effect; Gadolinium addition; Calcium Cobalt Oxides Mixed; Calcium Oxides; Manufacturing; Electroceramics
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-008-2990-6

A series of Ca
3−
x
Gd
x
Co
4
O
9+δ
precursor powders were synthesized by the polyacrylamide gel method, and their ceramics were obtained by the Spark Plasma Sintering (SPS). There were lots of defects in the sheet-like grains from SEM and TEM observations. The electrical and the thermal transport properties were obviously affected by the material microstructure. The small polaron hopping conduction mechanism was determined above 600 K, and the hopping activation energy increased with the increase of doping contents. It was found that the Seebeck coefficient and the resistivity of doped samples were markly enhanced due to the impurity compensation effect, and their thermal conductivities were decreased due to the defects scattering. The maximum figure of merit of
ZT
 = 0.24 at 973 K was obtained for Ca
2.7
Gd
0.3
Co
4
O
9+δ
.