Phase Purity and Thermoelectric Properties of Type-I Clathrates Ba₈Cu_xSi_yGe_46-x-y (4 ≤ x ≤ 6.5, y = 0 and 5.15 ≤ x ≤ 6.425, 2.05≤ y ≤ 36.9)

Abstract:

Type-I clathrates have been considered as very promising thermoelectric (TE) materials thus attracting attention widely. Here we report new clathrates Ba₈Cu_xSi_yGe_46-x-y (4≤ x ≤ 6.5, y = 0 and 5.15 ≤ x ≤ 6.425, 2.05≤ y ≤ 36.9), focusing on their phase purity and TE properties. Our results show that samples prepared by arc melting followed by annealing are multi-phases alloys. The composition of the clathrate phase is also inhomogeneous. This indicates that the kinetic factor dominates the reaction of forming the clathrate phase during element-melting and sample-annealing. We select three compositions in these two series of samples, which have less impurity and better composition homogeneity for the clathrate phase, and the annealed alloys are furthered processed by ball milling (BM) and powder-solidification (either by hot pressing (HP) or by spark plasma sintering (SPS)) for TE properties investigations. The BM and HP/SPS processes can improve the phase purity and homogeneity. The TE measurements show that the Si-substituted samples have better performance than the Ge-based sample, mainly by decreasing the electrical resistivity. This indicates that the elemental substitution may be still an effective way to improve the TE performance of clathrates.

• Periodical: Advanced Materials Research (Volume 1142)
• Pages: 37-44
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1142.37
• Online since: January 2017
• Authors: Yue Dong, Xin Lin Yan, Zhao Hui Tang, Xue Yong Ding, Xu Dong Sun, S. Paschen
• Keywords: Clathrates, Figure of Merit, Thermoelectric Materials

References

[1] I.B. Cadoef, E. Miller, Thermoelectric Materials and Device, Reinhold, New York, (1960).

[2] D.M. Rowe, C.M. Bhandari, Modern Thermoelectrics, Reston, VA, (1983).

[3] F. Ioefe, Semiconductors Thermoelements and Thermoelectric Cooling, Interscince, New York-London, (1961).

[4] C. Wood, Materials for thermoelectric energy conversion, Rep. Prog. Phys. 51 (1988) 459-539.

[5] E.B. Lon, Cooling, heating, generating power, and recovering waste heat with thermoelectric systems, Science 321 (2008) 1457-1461.

DOI: 10.1126/science.1158899

[6] F.J. Disalvo, Thermoelectric cooling and power generation, Science 285 (1999) 703-706.

DOI: 10.1126/science.285.5428.703

[7] H.J. Goldsmid, Thermoelectric Refrigeration, Plenum, New York, (1964).

[8] D.M. Rowe, CRC Handbook of Thermoelectrics, CRC, Boca Raton, (1995).

[9] T.M. Tritt, Recent Trends in Thermoelectric Materials Research III, Academic, San Diego, (2001).

[10] D.D. Pollok, Thermocouples: Theory and Properties, CRC, Boca Raton, (1991).

[11] B.C. Sales, Smaller is cooler, Science 295 (2002) 1248-1249.

[12] G. Mahan, B. Sales, J. Sharp, Thermoelectric materials: new approaches to an old problem, Phys. Today 50 (2008) 42-47.

DOI: 10.1063/1.881752

[13] C.B. Vining, A model for the high-temperature transport properties of heavily doped n-type silicon-germanium alloys, J. Appl. Phys. 69 (1991) 331-334.

DOI: 10.1063/1.347717

[14] J. Yang, T. Caillat, Thermoelectric materials for space and automotive power generation, MRS Bull. 31 (2006) 224-229.

DOI: 10.1557/mrs2006.49

[15] G.S. Nolas, J. Poon, M. Kanatzidis, Recent developments in bulk thermoelectric materials, MRS Bull. 31 (2006) 199-205.

DOI: 10.1557/mrs2006.45

[16] D.M. Rowe, Thermoelectrics, an environmentally-friendly source of electrical power, Renew. Energ. 16 (1999) 1251-1256.

DOI: 10.1016/s0960-1481(98)00512-6

[17] D.M. Rowe, Thermoelectrics Handbook: Macro to Nano, CRC/Taylor & Francis, Boca Raton, (2006).

[18] T.M. Tritt, M.A. Subramanian, Thermoelectric materials, phenomena, and applications: a bird's eye view, MRS Bull. 31 (2006) 188-198.

DOI: 10.1557/mrs2006.44

[19] H.J. Goldsid, G.S. Nolas, A review of the new thermoelectric materials, in: Proc. 20th Inter. Conf. Thermoelectrics, Beijing, R.P. China, Jun 8-11 2001, pp.1-6.

[20] G.S. Nolas, J.L. Cohn, G.A. Slack, S.B. Schujman, Semiconducting Ge clathrates: Promising candidates for thermoelectric applications, Appl. Phys. Lett. 73 (1998) 178-180.

DOI: 10.1063/1.121747

[21] B.C. Sales, B.C. Chakoumakos, R. Jin, J.R. Thompson, D. Mandrus, Structural, magnetic, thermal, and transport properties of X8Ga16Ge30 (X=Eu, Sr, Ba) single crystals, Phys. Rev. B 63 (2001) 245113.

[22] Y. Jiang, F. Bridges, M.A. Avila, T. Takabatake, J. Guzman, G. Kurczveil, EXAFS study of n- and p-type Ba8Ga16Ge30, Phys. Rev. B 78 (2008) 014111.

[23] H. Schäfer, On the problem of polar intermetallic compounds: the stimulation of E. Zintl's work for the modern chemistry of intermetallics, Annu. Rev. Mater. Sci. 15 (1985) 1-42.

DOI: 10.1146/annurev.ms.15.080185.000245

[24] X. Yan, M. X. Chen, S. Laumann, E. Bauer, P Rog, R. Podloucky, S. Paschen, Thermoelectric properties of Ba-Cu-Si clathrates, Phys. Rev. B 85 (2012) 165127.

DOI: 10.1103/physrevb.85.165127

[25] X. Yan, A. Grytsiv, G. Giester, E. Bauer, P. Rogl, S. Paschen, Single-crystal investigations on quaternary clathrates Ba8Cu5SixGe41-x (x=6, 18, 41), J. Electron. Mater. 40 (2011) 589-596.

DOI: 10.1007/s11664-010-1464-1