Multi-doping in SnTe: Improvement of Thermoelectric Performance due to Lower Thermal Conductivity and Enhanced Power Factor

doi:10.15541/jim20180273

Abstract

Abstract:

In recent years, tin telluride (SnTe) has attracted considerable interest due to its potential thermoelectric application as a lead-free rock-salt analogue of PbTe. However, pristine SnTe samples show high thermal conductivity and low Seebeck coefficients, resulting in poor thermoelectric performance. In this study, the thermoelectric performance of SnTe was enhanced by well-designed multi-doping, where significantly reduced thermal conductivity and improved Seebeck coefficientswere achieved at the same time. The doped SnTe samples were prepared by hot pressing. The lattice thermal conductivity of SnTe samples is obviously decreased by alloying with Se and S. The transmission electron microscope shows the existence of larger amount of nano-precipitates and the lattice distortions in the alloyed samples. For example, the lattice thermal conductivity of SnTe_0.7S_0.15Se_0.15 sample is reduced to 0.99 W•m^-1•K^-1 at 300 K. The results reveal that the Seebeck coefficients are improved by introducing In resonant state in the band structure of SnTe. The experiments suggest the effectiveness of designed multi-doping in the thermoelectric performance enhancement of SnTe, and a promising ZT of 0.8 at 850 K is achieved in Sn_0.99In_0.01Te_0.7S_0.15Se_0.15. The discovery suggests that SnTe is a promising medium-temperature thermoelectric candidate.

Key words: tin telluride, thermoelectric performance, resonant state, lattice thermal conductivity

CLC Number:

TQ174

TAN Xiao-Fang, DUAN Si-Chen, WANG Hong-Xiang, WU Qing-Song, LI Miao-Miao, LIU Guo-Qiang, XU Jing-Tao, TAN Xiao-Jian, SHAO He-Zhu, JIANG Jun. Multi-doping in SnTe: Improvement of Thermoelectric Performance due to Lower Thermal Conductivity and Enhanced Power Factor[J]. Journal of Inorganic Materials, 2019, 34(3): 335-340.

Figures/Tables 10

Fig.1 Temperature-dependent (a) total thermal conductivities(κtot) and (b) lattice thermal conductivities (κlat) of SnTe1-2xSxSex (x = 0, 0.05, 0.1, and 0.15) samples

Fig. 2 Temperature-dependent (a) total thermal conductivities(κtot) and (b) lattice thermal conductivities (κlat) of Sn1-yInyTe0.7S0.15Se0.15 (y=0, 0.0025, 0.005, 0.01, and 0.015) samples

Fig.3 Microstructures of Sn0.99In0.01Te0.7S0.15Se0.15(a) Medium-magnification TEM and (b) low-magnification images show the presence of nanoscale secondary phase; The inset in (a) is the SAED pattern along [004]; (c) HRTEM image focusing on the secondary phase with distorted connection between the precipitate and the matrix; The top-right and bottom-right insets are the respective FFT images showing lattice distortion between them; (d) the same TEM image with (c) showing the IFFT image (the bottom-right inset) of the selected region reflecting lattice distortion; and strain maps reflect high strain states inside (e) and around (f) the precipitates

Fig.4 Temperature dependent thermoelectric properties: (a) electrical conductivity σ, (b) the Seebeck coefficients S,(c) the power factors S2σ, and (d) ZT values for Sn1-yInyTe0.7S0.15Se0.15 (y=0, 0.0025, 0.005, 0.01, and 0.015) samples

Table 1 The density ρ, hole concentration n, mobility μ, electrical conductivity σ, Seebeck coefficient S, and power factor S2σ for Sn1-yInyTe0.7S0.15Se0.15 (y=0, 0.0025, 0.005, 0.01, and 0.015) samples at room temperature

Samples	ρ/(g•cm^-3)	N/(× 10²⁰, cm^-3)	μ/(cm²•V^-1•s^-1)	σ/(S•cm^-1)	S/(μV•K^-1)	S²σ/(μW•cm^-1•K^-2)
y=0	6.247	1.3	164	3480	7.6	0.2
y=0.0025	6.209	1.4	100	2300	34	2.7
y=0.005	6.161	1.6	57	1510	50	3.7
y=0.01	6.161	2.0	39	1240	63	4.9
y=0.015	6.195	2.2	26	910	71	4.6

Fig.S1 Room temperature (a) powder XRD patterns, (b) lattice parameter of SnTe1-2xSxSex (x=0, 0.05, 0.1, and 0.15) samples

Fig.S2 Temperature dependent (a) electrical conductivity and (b) Seebeck coefficient of SnTe1-2xSxSex (x=0, 0.05, 0.1, and 0.15) samples

Fig.S3 Room temperature (a) powder XRD patterns, (b) lattice parameter a, (c) Hall carrier density Np, and (d) carrier mobility μ of Sn1-yInyTe0.7S0.15Se0.15 (y=0, 0.0025, 0.005, 0.01, and 0.015) samples

Fig.S4 Temperature dependent heat diffusivity of Sn1-yInyTe0.7S0.15Se0.15 (y=0, 0.0025, 0.005, 0.01, and 0.015) samples

Fig.S5 Room temperature Pisarenko plot for Sn1-yInyTe0.7(SeS)0.15 (y=0,0.0025,0.005,0.01,0.015). The solid curve is experted from Zhang[18]

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