Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C.
This journal is © The Royal Society of Chemistry 2015
Electronic Supplementary Information
for
Enhanced average thermoelectric figure of merit of n-type PbTe1−xIx–MgTe
Priyanka Jood,a Michihiro Ohta,†,a Masaru Kunii,a
Xiaokai Hu,a Hirotaka Nishiate,a Atsushi
Yamamoto,a and Mercouri G. Kanatzidisb,c
aResearch
Institute for Energy Conservation, National Institute of Advanced Industrial Science and
Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan. *E-mail: ohta.michihiro@aist.go.jp
bDepartment
cMaterials
of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
Science Division, Argonne National Laboratory, Argonne, Illinois 60439,USA.
Fig. S1
Temperature dependences of (a) thermal diffusivity (D), and heat capacity (CP) for PbTe1-xIx-yMgTe
(0.0012 ≤ x ≤ 0.006; y = 0 and 1 mol%).
Fig. S2
Temperature dependence of the (a) electrical resistivity (ρ), Seebeck coefficient (S), (b) total thermal
conductivity (κtotal), and thermoelectric figure of merit (ZT) for PbTe0.9972I0.0028–2 mol% MgTe.
Fig. S3
Zoom-in powder X-ray diffraction patterns of PbTe0.9972I0.0028–yMgTe (y = 0, 1 and 2 mol%) showing
the onset of peak splitting in PbTe0.9972I0.0028–2% MgTe
Fig. S4
Log-log plot of electrical resistivity and temperature for PbTe1−xIx–yMgTe (x = 0.004 and 0.006; y= 0
and 1 mol%)
The Lorenz number can be expressed as a function of the reduced chemical potential (η) for a single
parabolic band:
𝐿=
𝑘𝑏 3𝐹0(𝜂)𝐹2(𝜂) ‒ 4𝐹1(𝜂)2
()
2
𝐹0(𝜂)2
𝑒
(1),
where 𝑘𝑏 and 𝑒 are Boltzmann constant and elementary charge, respectively.
η was obtained from the fitting of the experimental S values using the following equation for the
single parabolic band model dominated by acoustic phonon scattering.
𝑆=
𝑘𝑏 2𝐹1(𝜂)
(
𝑒 𝐹0(𝜂)
‒𝜂
)
(2),
where the Fermi integrals Fm(η) are defined as:
∞
𝐹𝑚(𝜂) =
∫
0
𝑥𝑚
𝑑𝑥
1 + 𝑒𝑥𝑝⁡(𝑥 ‒ 𝜂)
(3).
The temperature dependence of the calculated L from the fitting procedure for PbTe1−xIx–yMgTe
(0.0012 ≤ x ≤ 0.006; y = 0 and 1 mol%) is given in Fig. S5
Fig. S5
Temperature dependence of the calculated Lorenz number (L) for PbTe1−xIx–yMgTe (0.0012 ≤ x ≤
0.006; y = 0 and 1 mol%)
Table S1
Room-temperature electron mobility (μ) and carrier concentration (n) for PbTe1−xIx–yMgTe (0.0012 ≤
x ≤ 0.006; y = 0 and 1 mol%)
Sample
μ (cm2 V−1 s−1) n (1019 cm−3)
x= 0.0012
296
1.62
x= 0.0012, 1% MgTe
327
1.31
x= 0.0028
168
2.27
x= 0.0028, 1% MgTe
403
1.63
x= 0.0028, 2% MgTe
164
0.38
x= 0.0040,
610
4.05
x= 0.0040, 1% MgTe
451
2.24
x= 0.0060
538
7.40
x= 0.0060, 1% MgTe
436
5.73
Table S2
Density (d) of the sintered compacts of PbTe1−xIx–yMgTe (0.0012 ≤ x ≤ 0.006; y = 0 and 1 mol%)
measured using Gas pycnometer method.
Sample
d (g cm-3)
x= 0.0012
8.20
x= 0.0012, 1% MgTe
8.18
x= 0.0028
8.20
x= 0.0028, 1% MgTe
8.17
x= 0.0040
8.16
x= 0.0040, 1% MgTe
8.09
x= 0.0060
8.14
x= 0.0060, 1% MgTe
8.07