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Title: Heat capacity of Mg 3Sb 2, Mg 3Bi 2, and their alloys at high temperature

Abstract

The thermoelectric figure of merit reported for n-type Mg 3(Sb,Bi) 2 compounds has made these materials of great engineering significance, increasing the need for accurate evaluations of their thermal conductivity. Thermal conductivity is typically derived from measurements of thermal diffusivity and determination of the specific heat capacity. The uncertainty in this method (often 10% or more) is frequently attributed to measurement of heat capacity such that estimated values are often more accurate. Inconsistencies between reported thermal conductivity of Mg 3(Sb,Bi) 2 compounds may be attributed to the different values of heat capacity measured or used to calculate thermal conductivity. The high anharmonicity of these materials can lead to significant deviations at high temperatures from the Dulong-Petit heat capacity, which is often a reasonable substitute for measurements at high temperatures. Herein, a physics-based model is used to assess the magnitude of the heat capacity over the entire temperature range up to 800 K. The model agrees in magnitude with experimental low-temperature values and reproduces the linear slope observed in high-temperature data. Owing to the large scatter in experimental values of high-temperature heat capacity, the model is likely more accurate (within ±3%) than a measurement of a new sample even for dopedmore » or alloyed materials. It is found that heat capacity for the solid solution series can be simply described (for temperatures: 200K≤T≤800K ) by the polynomial equation: c p[Jg –1K –1]=3NR/M W(1 + 1.3 × 10 –4 T – 4 × 10 3 T –2), where 3 NR = 124.71 J mol –1K –1, MW is the molecular weight [gmol –1] of the formula unit being considered, and T is temperature in K. This heat capacity is recommended to be a standard value for reporting and comparing the thermal conductivity of Mg 3(Sb,Bi) 2 including doped or alloyed derivatives. Furthermore, a general form of the equation is given which can be used for other material systems« less

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [2];  [2];  [3];  [4];  [4];  [5];  [1]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Jet Propulsion Lab./California Inst. of Technology (CalTech), Pasadena, CA (United States)
  3. Michigan State Univ., East Lansing, MI (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Argonne National Lab. (ANL), Argonne, IL (United States); Northwestern Univ., Evanston, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1489260
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Materials Today Physics
Additional Journal Information:
Journal Volume: 6; Journal Issue: C; Journal ID: ISSN 2542-5293
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Heat capacity; Mg3Bi2; Mg3Sb2; Thermal conductivity; Thermoelectric

Citation Formats

Agne, Matthias T., Imasato, Kazuki, Anand, Shashwat, Lee, Kathleen, Bux, Sabah K., Zevalkink, Alex, Rettie, Alexander J. E., Chung, Duck Young, Kanatzidis, Mercouri G., and Snyder, G. Jeffrey. Heat capacity of Mg3Sb2, Mg3Bi2, and their alloys at high temperature. United States: N. p., 2018. Web. doi:10.1016/j.mtphys.2018.10.001.
Agne, Matthias T., Imasato, Kazuki, Anand, Shashwat, Lee, Kathleen, Bux, Sabah K., Zevalkink, Alex, Rettie, Alexander J. E., Chung, Duck Young, Kanatzidis, Mercouri G., & Snyder, G. Jeffrey. Heat capacity of Mg3Sb2, Mg3Bi2, and their alloys at high temperature. United States. doi:10.1016/j.mtphys.2018.10.001.
Agne, Matthias T., Imasato, Kazuki, Anand, Shashwat, Lee, Kathleen, Bux, Sabah K., Zevalkink, Alex, Rettie, Alexander J. E., Chung, Duck Young, Kanatzidis, Mercouri G., and Snyder, G. Jeffrey. Sat . "Heat capacity of Mg3Sb2, Mg3Bi2, and their alloys at high temperature". United States. doi:10.1016/j.mtphys.2018.10.001.
@article{osti_1489260,
title = {Heat capacity of Mg3Sb2, Mg3Bi2, and their alloys at high temperature},
author = {Agne, Matthias T. and Imasato, Kazuki and Anand, Shashwat and Lee, Kathleen and Bux, Sabah K. and Zevalkink, Alex and Rettie, Alexander J. E. and Chung, Duck Young and Kanatzidis, Mercouri G. and Snyder, G. Jeffrey},
abstractNote = {The thermoelectric figure of merit reported for n-type Mg3(Sb,Bi)2 compounds has made these materials of great engineering significance, increasing the need for accurate evaluations of their thermal conductivity. Thermal conductivity is typically derived from measurements of thermal diffusivity and determination of the specific heat capacity. The uncertainty in this method (often 10% or more) is frequently attributed to measurement of heat capacity such that estimated values are often more accurate. Inconsistencies between reported thermal conductivity of Mg3(Sb,Bi)2 compounds may be attributed to the different values of heat capacity measured or used to calculate thermal conductivity. The high anharmonicity of these materials can lead to significant deviations at high temperatures from the Dulong-Petit heat capacity, which is often a reasonable substitute for measurements at high temperatures. Herein, a physics-based model is used to assess the magnitude of the heat capacity over the entire temperature range up to 800 K. The model agrees in magnitude with experimental low-temperature values and reproduces the linear slope observed in high-temperature data. Owing to the large scatter in experimental values of high-temperature heat capacity, the model is likely more accurate (within ±3%) than a measurement of a new sample even for doped or alloyed materials. It is found that heat capacity for the solid solution series can be simply described (for temperatures: 200K≤T≤800K ) by the polynomial equation: cp[Jg–1K–1]=3NR/MW(1 + 1.3 × 10–4 T – 4 × 103 T–2), where 3NR = 124.71 J mol–1K–1, MW is the molecular weight [gmol–1] of the formula unit being considered, and T is temperature in K. This heat capacity is recommended to be a standard value for reporting and comparing the thermal conductivity of Mg3(Sb,Bi)2 including doped or alloyed derivatives. Furthermore, a general form of the equation is given which can be used for other material systems},
doi = {10.1016/j.mtphys.2018.10.001},
journal = {Materials Today Physics},
issn = {2542-5293},
number = C,
volume = 6,
place = {United States},
year = {2018},
month = {11}
}

Journal Article:
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