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 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: c p [Jg −1 K −1 ]=[Formula presented](1+1.3×10 −4 T−4×10 3 T −2 ),where 3NR=124.71Jmol −1 K −1 , M W 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. A general form of the equation is given which can be used for other material systems.
| Original language | English |
|---|---|
| Pages (from-to) | 83-88 |
| Number of pages | 6 |
| Journal | Materials Today Physics |
| Volume | 6 |
| DOIs | |
| Publication status | Published - Aug 1 2018 |
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Keywords
- Heat capacity
- Mg Bi
- Mg Sb
- Thermal conductivity
- Thermoelectric
ASJC Scopus subject areas
- Materials Science(all)
- Physics and Astronomy (miscellaneous)
- Energy (miscellaneous)
Cite this
Heat capacity of Mg 3 Sb 2 , Mg 3 Bi 2 , and their alloys at high temperature . / 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.
In: Materials Today Physics, Vol. 6, 01.08.2018, p. 83-88.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Heat capacity of Mg 3 Sb 2 , Mg 3 Bi 2 , and their alloys at high temperature
AU - Agne, Matthias T.
AU - Imasato, Kazuki
AU - Anand, Shashwat
AU - Lee, Kathleen
AU - Bux, Sabah K.
AU - Zevalkink, Alex
AU - Rettie, Alexander J.E.
AU - Chung, Duck Young
AU - Kanatzidis, Mercouri G
AU - Snyder, G. Jeffrey
PY - 2018/8/1
Y1 - 2018/8/1
N2 - 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 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: c p [Jg −1 K −1 ]=[Formula presented](1+1.3×10 −4 T−4×10 3 T −2 ),where 3NR=124.71Jmol −1 K −1 , M W 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. A general form of the equation is given which can be used for other material systems.
AB - 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 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: c p [Jg −1 K −1 ]=[Formula presented](1+1.3×10 −4 T−4×10 3 T −2 ),where 3NR=124.71Jmol −1 K −1 , M W 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. A general form of the equation is given which can be used for other material systems.
KW - Heat capacity
KW - Mg Bi
KW - Mg Sb
KW - Thermal conductivity
KW - Thermoelectric
UR - http://www.scopus.com/inward/record.url?scp=85055578832&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85055578832&partnerID=8YFLogxK
U2 - 10.1016/j.mtphys.2018.10.001
DO - 10.1016/j.mtphys.2018.10.001
M3 - Article
VL - 6
SP - 83
EP - 88
JO - Materials Today Physics
JF - Materials Today Physics
SN - 2542-5293
ER -