Influence of Ge1-xInxTe Microstructure on Thermoelectric Properties

doi:10.15541/jim20190641

Abstract

Abstract:

The resonant levels can be introduced into GeTe by In element, however, the effect of its microstructure on thermoelectric properties still remained unclear. In this study, a series of Ge_1-_xIn_xTe samples were prepared by smelting-quenching-annealing combined with spark plasma sintering (SPS). The XRD, SEM, laser thermal conductivity instrument and thermoelectric performance analysis system (ZEM-3) were applied to study the microstructure and thermoelectric properties. Results show that, with the incorporation of In content, the unit cell volume decreases, and Herringbone structure has become smaller and grain boundaries increase, which result in a decrease in the lattice thermal conductivity. Thereby, a minimum thermal conductivity of 2.16 W·m ^-1·K ^-1 is obtained. Meanwhile, In doping introduces the resonant levels and decreases the carrier concentration, so the Seebeck coefficient and the power factor increase. Consequently, the maximum ZT value of 1.15 is obtained in the 0.03 sample at 600 K, which is 26.4% higher than that of GeTe. This indicates that the thermoelectric properties of Ge_1-_xIn_xTe can be effectively improved by the microstructure regulation.

Key words: In doping, thermal conductivity, GeTe, thermoelectric materials

CLC Number:

TB34
O472

QIU Xiaoxiao,ZHOU Xiying,FU Yuntian,SUN Xiaomeng,WANG Lianjun,JIANG Wan. Influence of Ge_1-_xIn_xTe Microstructure on Thermoelectric Properties[J]. Journal of Inorganic Materials, 2020, 35(8): 916-922.

Figures/Tables 10

Fig. 1 XRD patterns of Ge1-xInxTe compounds (a) Before SPS; (b) After SPS

Table 1 Lattice parameters and volume of Ge1-xInxTe

x	a/nm	b/nm	c/nm	V/nm³
0	0.4165	0.4165	1.0667	0.160284
0.01	0.4167	0.4167	1.0656	0.160234
0.02	0.4170	0.4170	1.0639	0.160204
0.03	0.4173	0.4173	1.0627	0.160278
0.05	0.4175	0.4175	1.0604	0.160037
0.10	0.4192	0.4192	1.0449	0.159058

Fig. 2 XPS patterns of Ge1-xInxTe (a) Full scan spectrum; (b) Binding energy of Ge3d; (c) Binding energy of In3d; (d) Binding energy of Te3d

Fig. 3 EDS mapping of the elements in Ge0.97In0.03Te (a)Fractured surface of Ge0.97In0.03Te; (b-d) Corresponding compositional mapping

Table 2 Information of different elements of Ge0.97In0.03Te

Element	Atomic number	Mass/ %	Normalized quality/%	Atom/ %	Abs. error/ %
Te	52	64.25	64.28	50.38	1.89
Ge	32	34.24	34.26	47.18	1.91
In	49	1.43	1.46	1.27	0.07

Fig. 4 Fructure surface SEM images of Ge1-xInxTe (a) x=0; (b)x=0.01; (c) x=0.02; (d) x=0.03; (e)x=0.05; (f) x=0.10

Table 3 Electrical transport properties of Ge1-xInxTe at room temperature

Sample	ρ/(g·cm^-3)	d/%	σ/(×10⁴, S·m^-1)	S/(μV·K^-1)	n_H/(×10²⁰, cm^-3)	m_H/(cm²·V^-1·s^-1)	L₀/(×10^-8, V²·K^-2)
x=0	6.176	99.27	74.92	38.4	16.32	35.31	2.22
x =0.005	6.168	99.00	54.75	49.7	—	—	2.15
x =0.010	6.184	99.16	49.75	54.5	—	—	2.13
x =0.015	6.193	99.20	37.72	64.3	13.05	25.44	2.07
x =0.020	6.185	98.95	30.61	66.8	—	—	2.05
x =0.025	6.170	98.59	26.80	77.9	—	—	2.01
x =0.030	6.183	98.75	22.49	86.0	10.55	22.54	1.98
x =0.050	6.162	97.86	11.47	125	9.818	12.40	1.84
x =0.100	6.240	97.48	1.02	267	4.083	5.521	1.60

Fig. 5 Thermoelectric properties of Ge1-xInxTe (a) Electrical conductivity; (b) Seebeck coefficient; (c) Power factor; (d) Total thermal conductivity; (e) Lattice thermal conductivity; (f) Figure of merit

Fig. 6 Heat capacity of Ge1-xInxTe

Fig. 7 Mechanism of the effect of structure on thermoelectric performance

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