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Thermoelectric power factor enhancement of textured ferroelectric SrxBa1–x Nb2O6–δ ceramics

Published online by Cambridge University Press:  14 January 2011

Soonil Lee ,
Sinan Dursun ,
Cihangir Duran  and
Clive A. Randall
Soonil Lee*
Affiliation:
Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802
Sinan Dursun
Affiliation:
Gebze Institute of Technology, Department of Materials Science and Engineering, Gebze, Kocaeli 41400, Turkey
Cihangir Duran
Affiliation:
Gebze Institute of Technology, Department of Materials Science and Engineering, Gebze, Kocaeli 41400, Turkey
Clive A. Randall
Affiliation:
Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802
*
a)Address all correspondence to this author. e-mail: leesoonil@gmail.com
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Abstract

A promising n-type thermoelectric oxide, based on the tungsten bronze-structured ferroelectric SrxBa1–xNb2O6–δ (SBN, x~0.61), was investigated to enhance the thermoelectric power factor through templated grain growth (textured polycrystalline). In the reduced SBN textured, both the electrical conductivity (σ) and the magnitude of thermopower (S) are increased in the c axis: σ33 > σ11 and |S33| > |S11|, and consequently, the thermoelectric power factor (PF) increased significantly due to crystal anisotropy and grain boundary density reduction. It was found in randomly oriented polycrystalline ceramics that the thermoelectric properties are dominated by a-axis properties. A ferroelectric–thermoelectric anomaly is observed at 4mm–4/mmm phase transition temperature (TC) and depends on temperature and reduction degree, consistent with our earlier observations in single crystal SBN. Above TC, the carrier transport mechanism is controlled by polaron hopping conduction, and below TC the behavior depends on the degree of reduction. However, the magnitude of the Seebeck coefficient is dependent on the crystal anisotropy.

Keywords

ThermoelectricDefectsTexture

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Type
Articles
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Journal of Materials Research , Volume 26 , Issue 1 , 14 January 2011 , pp. 26 - 30
Copyright
Copyright © Materials Research Society 2011

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