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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*
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: [email protected]
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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.

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Articles
Copyright
Copyright © Materials Research Society 2011

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References

REFERENCES

1.Goldsmid, H.J.: Thermoelectric Refrigeration (Plenum, New York, 1964).CrossRefGoogle Scholar
2.Terasaki, I., Sasago, Y., and Uchinokura, K.: Large thermoelectric power in NaCo2O4 single crystals. Phys. Rev. B 56, 12685 (1997).CrossRefGoogle Scholar
3.Lee, S., Wilke, R.H.T., Trolier-McKinstry, S., Zhang, S., and Randall, C.A.: Sr xBa1– xNb2O6–δ ferroelectric-thermoelectrics: Crystal anisotropy, conduction mechanism, and power factor. Appl. Phys. Lett. 96, 031910 (2010).CrossRefGoogle Scholar
4.Duran, C., Trolier-McKinstry, S., and Messing, G.L.: Fabrication and electrical properties of textured Sr0.53Ba0.47Nb2O6 ceramics by templated grain growth. J. Am. Ceram. Soc. 83, 2203 (2000).CrossRefGoogle Scholar
5.Duran, C., Trolier-McKinstry, S., and Messing, G.L.: Dielectric and piezoelectric properties of textured Sr0.53Ba0.47Nb2O6 ceramics prepared by templated grain growth. J. Mater. Res. 18, 228 (2003).Google Scholar
6.Jamieson, P.B., Abrahams, S.C., and Bernstel, J.L.: Ferroelectric tungsten bronze-type crystal structures. I. Barium strontium niobate Ba0.27Sr0.75Nb2O5.78. J. Chem. Phys. 48, 5048 (1968).CrossRefGoogle Scholar
7.Bursill, L.A. and Lin, P.J.: Incommensurate superstructures and phase transition of strontium barium niobate (SBN). Acta Crystallogr., Sect. B 43, 49 (1987).CrossRefGoogle Scholar
8.Woike, T., Petricek, V., Dusek, M., Hansen, N.K., Fertey, P., Lecomte, C., Arakcheeva, A., Chapuis, G., Imlau, M., and Pankrath, R.: The modulated structure of Ba0.39Sr0.61Nb2O6. I. Harmonic solution. Acta Crystallogr., Sect. B 59, 28 (2003).CrossRefGoogle ScholarPubMed
10.Ohta, H.: Thermoelectrics based on strontium titanate. Mater. Today 10, 44 (2007).CrossRefGoogle Scholar
11.Thiagarajan, S.J., Jovovic, V., and Heremans, J.P.: On the enhancement of the figure of merit in bulk nanocomposites. Phys. Status Solidi 1, 256 (2007) (RRL).Google Scholar
12.Meyers, M.A. and Inal, O.T.: Frontiers in Materials Technologies (Elsevier, Amsterdam, The Netherlands, 1985).Google Scholar
13.Snyder, G.J. and Toberer, E.S.: Complex thermoelectric materials. Nat. Mater. 7, 105 (2008).CrossRefGoogle ScholarPubMed
14.Messing, G.L., Trolier-McKinstry, S., Sabolsky, E.M., Duran, C., Kwon, S., Brahmaroutu, B., Park, P., Yilmaz, H., Rehrig, P.W., Eitel, K.B., Suvaci, E., Seabaugh, M., and Oh, K.S.: Templated grain growth of textured piezoelectric ceramics. Crit. Rev. Solid State Mater. Sci. 29, 45 (2004).CrossRefGoogle Scholar
15.Lotgering, F.K.: Topotactical reacting with ferrimagnetic oxides having hexagonal crystal structures-I. J. Inorg. Nucl. Chem. 9, 113 (1959).CrossRefGoogle Scholar
16.Ballman, A.A. and Brown, H.: The growth and properties of strontium barium metaniobate, Sr1– xBa xNb2O6, a tungsten bronze ferroelectric. J. Cryst. Growth 1, 311 (1967).CrossRefGoogle Scholar
17.Lee, S., Yang, G., Wilke, R.H.T., Trolier-McKinstry, S., and Randall, C.A.: Thermopower in highly reduced n-type ferroelectric and related perovskite oxides and the role of heterogeneous nonstoichiometry. Phys. Rev. B 79, 134110 (2009).CrossRefGoogle Scholar
18.Kolodiazhnyi, T.: Insulator-metal transition and anomalous sign reversal of the dominant charge carriers in perovskite BaTiO3–δ. Phys. Rev. B 78, 045107 (2008).CrossRefGoogle Scholar
19.Heikes, R.R. and Ure, R.W. Jr.: Thermoelectricity: Science and Engineering (Interscience, New York, 1961), p. 77.Google Scholar
20.Chaikin, P.M. and Beni, G.: Thermopower in the correlated hopping regime. Phys. Rev. B 13, 647 (1976).CrossRefGoogle Scholar
21.Newnham, R.E.: Properties of Materials: Anisotropy, Symmetry, and Structure (Oxford University Press, New York, 2005), p. 239.Google Scholar