N- ve P-tip Katkılı Mg2Si1-xSnx Katı alaşımlarının termal iletkenliklerinin teorik calışması
Mg2Si1-xSnx katı alaşımları yüksek termoelektrik verimlilikleri sebebiyle 500 K’den 800 K’e kadar olan orta sıcaklılık aralığı için umut vaadeden termoelektrik materyallerdir. Bu çalışmada hem n- hem p-tip katkılı Mg2Si1-xSnx katı alaşımlarının termal iletkenlikleri teorik olarak detaylıca incelenmesi sunulmuştur. Taşıyıcılardan (elektronlar yada holler), elektron-hole çiftlerinden ve fononlardan kaynaklanan termal iletkenlik katkıları ayrı ayrı göz önüne alınarak ve sırasıyla Wiedeman-Franz kanunu, Price’in teorisi, ve Debye’nin izotropik sürekli modeli uygulanarak hesaplanmıştır. Bütün fonon çarpışma mekanizmaları, kaynağı kristal sınırlarından, kütle bozukluklarından, bozunum potansiyellerinden ve anharmoniklikten olan katı alaşımların hepsi için eksiksiz bir şekilde incelenmiştir. En düşük toplam termal iletkenlik değerleri n-tip katkılı Mg2(Si0.4Sn0.6)0.98Bi0.02 katı alaşım için 700 K’de 2.431 WK-1 m-1 olarak, p-tip katkılı Mg2(Si0.3Sn0.7)0.95Ga0.05 katı alaşım için 600 K’de 1.843 WK-1 m-1 olarak bulunmuştur buda açıkca öneriyor ki p-tip katkılı Mg2Si1-xSnx tabanlı katı alaşımlar n-tip katkılı katı alaşımlarından termoelektrik cihazlar için daha iyi adaylardır.
Theoretical Study of Thermal Conductivities of n- and p-type Doped Mg2Si1-xSnx Thermoelectric Solid Solutions
Mg2Si1-xSnx solid solutions are a promising class of thermoelectric materials due to their high thermoelectric efficiencies at intermediate temperature range from 500 K to 800 K. Present study presents a theoretical work of the thermal conductivities of both n- and p-type doped Mg2Si1-xSnx solid solutions. The thermal conductivity contributions arising from carriers (electrons or holes), electron-hole pairs, and phonons are taken into account separately by employing the Wiedemann-Franz law, Price's theory, and Debye's isotropic continuum model, respectively. All phonon scattering mechanisms originate from crystal boundaries, mass-defects, deformation potentials, and anharmonicity are investigated rigorously for all solid solutions. The lowest total thermal conductivity values are obtained as 2.431 WK-1 m-1 at 700 K for n-type doped Mg2(Si0.4Sn0.6)0.98Bi0.02 solid solution and 1.843 WK-1 m-1 at 600 K for p-type doped Mg2(Si0.3Sn0.7)0.95Ga0.05 solid solution which clearly suggest that p-type doped Mg2Si1-xSnx based solid solutions are better candidates for the thermoelectric devices than their n-type doped solid solutions.
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- V. K. Zaitsev, M. I. Fedorov, I. S. Eremin,
E. A. Gurieva, and D. M. Rowe, ‘Thermoelectrics
handbook: macro to nano’, CRC Press. Taylor Fr.
Boca Rat., 2006.
- C. Li, Y. Wu, H. Li, and X. Liu,
‘Microstructural formation in
hypereutectic Al-Mg2Si with extra Si’, J.
Alloys Compd., vol. 477, no. 1, pp. 212–
216, 2009.
- P. M. Lee, ‘Electronic structure of
magnesium silicide and magnesium
germanide’, Phys. Rev., vol. 135, no. 4A,
p. A1110, 1964.
- S. K. Bux, M. T. Yeung, E. S. Toberer, G.
J. Snyder, R. B. Kaner, and J.-P. Fleurial,
‘Mechanochemical synthesis and
thermoelectric properties of high quality
magnesium silicide’, J. Mater. Chem., vol.
21, no. 33, pp. 12259–12266, 2011.
- V. K. Zaitsev et al., ‘Highly effective
Mg2Si1- xSnx thermoelectrics’, Phys. Rev.
B, vol. 74, no. 4, p. 45207, 2006.
- X. Liu et al., ‘Low electron scattering
potentials in high performance Mg2Si0.
45Sn0. 55 based thermoelectric solid
solutions with band convergence’, Adv.
Energy Mater., vol. 3, no. 9, pp. 1238–
1244, 2013.
- W. Liu et al., ‘High figure of merit and
thermoelectric properties of Bi-doped
Mg2Si0.4Sn0.6 solid solutions’, J. Solid
State Chem., vol. 203, pp. 333–339, 2013.
- T. Dasgupta, C. Stiewe, R. Hassdorf, A. J.
Zhou, L. Boettcher, and E. Mueller, ‘Effect
of vacancies on the thermoelectric
properties of Mg2Si1- xSbx (0 ≤ x ≤ 0.1)’,
Phys. Rev. B, vol. 83, no. 23, p. 235207,
2011.
- J.-Y. Jung, K.-H. Park, and I.-H. Kim,
‘Thermoelectric Properties of Sb-doped
Mg2Si Prepared by Solid-State Synthesis’,
IOP Conf. Ser. Mater. Sci. Eng., vol. 18,
no. 14, p. 142006, 2011.
- J. Tani and H. Kido, ‘Thermoelectric
properties of Sb-doped Mg2Si
semiconductors’, Intermetallics, vol. 15,
no. 9, pp. 1202–1207, 2007.
- M. I. Fedorov, V. K. Zaitsev, and G. N.
Isachenko, ‘High effective thermoelectrics
based on the Mg2Si-Mg2Sn solid solution’,
Solid State Phenomena, 2011, vol. 170, pp.
286–292.
- A. U. Khan, N. Vlachos, and T. Kyratsi,
‘High thermoelectric figure of merit of
Mg2Si0.55Sn0.4Ge0.05 materials doped with
Bi and Sb’, Scr. Mater., vol. 69, no. 8, pp.
606–609, 2013.
- P. J. Price, ‘CXXXV. Ambipolar
thermodiffusion of electrons and holes in
semiconductors’, London, Edinburgh,
Dublin Philos. Mag. J. Sci., vol. 46, no.
382, pp. 1252–1260, 1955.
- G. P. Srivastava, ‘The physics of phonons’,
CRC press, 1990.
- D. M. Rowe, ‘Thermoelectrics handbook:
macro to nano’, Thermoelectr. Handb.
Macro to Nano, vol. 80, no. 10, p. 1014,
2005.
- R. R. Heikes and R. W. Ure,
‘Thermoelectricity: science and
engineering’, Interscience Publishers,
1961.
- J. Tani and H. Kido, ‘Thermoelectric
properties of Bi-doped Mg2Si
semiconductors’, Phys. B Condens.
Matter, vol. 364, no. 1, pp. 218–224, 2005.
- T. Yi et al., ‘Synthesis and characterization
of Mg2Si/Si nanocomposites prepared
from MgH2 and silicon, and their
thermoelectric properties’, J. Mater.
Chem., vol. 22, no. 47, pp. 24805–24813,
2012.
- Ö. C. Yelgel and G. P. Srivastava,
‘Thermoelectric properties of n-type
Bi2(Te0.85Se0.15)3 single crystals doped with
CuBr and SbI3’, Phys. Rev. B, vol. 85, no.
12, p. 125207, 2012.
- A. H. Wilson, ‘The Theory of Metals
Cambridge’, Gt. Britain, p. 26, 1953.
- J. P. McKelvey, ‘Solid state and
semiconductor physics’, 1966.
- Ö. Ceyda Yelgel and G. P. Srivastava,
‘Thermoelectric properties of p-type
(Bi2Te3) x (Sb2Te3)1- x single crystals doped
with 3 wt.% Te’, J. Appl. Phys., vol. 113,
no. 7, p. 73709, 2013.
- G. S. Nolas, H. J. Goldsmid, and T. M.
Tritt, ‘Thermal Conductivity: Theory,
Properties, and Applications’, 2004.
- M. G. Holland, ‘Phonon scattering in
semiconductors from thermal conductivity
studies’, Phys. Rev., vol. 134, no. 2A, p.
A471, 1964.
- M. Grundmann, ‘The Physics of Phonons:
An Introduction Including Devices and
Nanophysics’. Springer, Berlin, 2006.
- O. Madelung, U. Rössler, and M. Schulz,
‘Non-tetrahedrally bonded elements and
binary compounds I’, Landolt-Börnstein
Ser., vol. 3, 1998.
- H. Wang, H. Jin, W. Chu, and Y. Guo,
‘Thermodynamic properties of Mg2Si and
Mg2Ge investigated by first principles
method’, J. Alloys Compd., vol. 499, no. 1,
pp. 68–4, 2010.