Preparation of p-type GeMnTe2 Based Thermoelectric Materials with Stable Cubic Phase

doi:10.15541/jim20250036

Abstract

Abstract:

p-type GeTe based thermoelectric (TE) materials have attracted significant attention owing to their remarkable TE performance in medium and low temperature range (300-800 K). However, the material undergoes a phase transition from rhombohedral to cubic in the temperature range of 600-700 K, inducing changes in the coefficient of thermal expansion that limit its application in TE devices. Consequently, it is imperative to develop stable GeTe based thermoelectric material free from phase transitions. In this study, high temperature melting combined with spark plasma sintering was employed to synthesize GeMnTe₂. The as-synthesized samples contain the secondary phase of MnTe₂, which increases total thermal conductivity from 1.34 W·m^-1·K^-1 to 1.81 W·m^-1·K^-1 at 800 K. By optimizing the chemical stoichiometry of different elements, the formation of MnTe₂ secondary phase is suppressed, resulting in stable pure cubic phase GeMnTe_1.96. GeMnTe_1.96 achieves a maximum zT of ~0.85 at 800 K. This TE material exhibits significant potential for efficient and stable waste heat utilization in the medium temperature range.

Key words: high temperature melting, cubic phase, GeMnTe₂ based compound, thermal conductivity

CLC Number:

TQ174

ZHANG Haifeng, JIANG Meng, SUN Tingting, WANG Lianjun, JIANG Wan. Preparation of p-type GeMnTe₂Based Thermoelectric Materials with Stable Cubic Phase[J]. Journal of Inorganic Materials, 2025, 40(11): 1245-1251.

Figures/Tables 5

Fig. 1 Room temperature crystal structures for (a) hexagonal MnTe, (b) rhombohedral GeTe and (c) cubic GeMnTe2; (d) Powder XRD patterns of GeMn1-xTe2-2x and GeMnTe2-y at room temperature;(e) Differential scanning calorimetry and thermogravimetric heat flow curves of GeMnTe1.96

Fig. 2 BSE images and surface scan EDS element distributions of (a) GeMnTe2, (b) GeMn0.98Te1.96 and (c) GeMnTe1.96 samples

Table 1 Element contents of the points in Fig. 2(a) by EDS point scanning (in atom)

Point	Mn/%	Ge/%	Te/%
1	34.39	4.04	61.56
2	34.50	/	65.50
3	34.74	5.76	59.49

Fig. 3 (a) FFT image along [$0\bar{1}1$] zone axes, (b) HRTEM image and (c) elemental distribution images for GeMnTe1.96 sample

Fig. 4 Temperature dependent (a) electrical resistivity, (b) Seebeck coefficient, (c) power factor, (d) total thermal conductivity, (e) lattice and electronic thermal conductivity, and (f) zT for GeMn1-xTe2-2x and GeMnTe2-y samples

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Preparation of p-type GeMnTe₂Based Thermoelectric Materials with Stable Cubic Phase

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