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Improved thermoelectric properties in Zn-doped Ca_(5)Ga_(2)Sb_6

Johnson, Samantha I. and Zevalkink, Alex and Snyder, G. Jeffrey (2013) Improved thermoelectric properties in Zn-doped Ca_(5)Ga_(2)Sb_6. Journal of Materials Chemistry A, 1 (13). pp. 4244-4249. ISSN 2050-7488. doi:10.1039/C3TA00844D.

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Zintl compounds with the chemical formula Ca_(5)M_(2)Sb_6 have attracted attention as candidates for use in thermoelectric applications due to their low thermal conductivity and promising high temperature performance (i.e., zT = 0.6 at 1000 K in Ca_(5)Al_(2−x)Na_(x)Sb_6). We have shown previously that, relative to Ca_(5)Al_(2)Sb_6, both Ca_(5)Ga_(2)Sb_6 and Ca_(5)In_(2)Sb_6 have reduced phonon velocities and improved carrier mobility, suggesting that improved zT can be achieved in these materials. Here we further investigate Ca_(5)Ga_(2)Sb_6, which is an intrinsic semiconductor with a small concentration of p-type carriers. By substituting Zn^2+ on the Ga^3+ site, we show that it is possible to increase and control the carrier concentration in Ca_(5)Ga_(2−x)Zn_(x)Sb_6 and thus optimize its thermoelectric behavior. A single parabolic band model was used to estimate an effective mass of m* = 1.6me, which is slightly lower than Al-based compounds. Though the reduced m* leads to a lower Seebeck coefficient, it also leads to a much higher electronic mobility. The high mobility leads to increased thermoelectric figure of merit (zT) at low and intermediate temperatures relative to Zn-doped Ca5Al2Sb6. However, due to the decreased band gap in Ca_(5)Ga_(2)Sb_6 relative to Ca5Al2Sb6, the maximum zT in optimally doped Ca_(5)Ga_(2)Sb_6 is reduced (peak zT ~ 0.35 at T = 775 K).

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Snyder, G. Jeffrey0000-0003-1414-8682
Additional Information:© 2013 Royal Society of Chemistry. Received 26th October 2012; Accepted 4th February 2013. First published on the web 18 Feb 2013. We would like to thank the Jet Propulsion Laboratory and the National Science Foundation for their generous support.
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Issue or Number:13
Record Number:CaltechAUTHORS:20130404-153700201
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37770
Deposited On:05 Apr 2013 17:36
Last Modified:09 Nov 2021 23:31

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