Effect of Rare-earth Variable-valence Element Eu doping on Thermoelectric Property of BiCuSeO

doi:10.15541/jim20190570

Abstract

Abstract:

As a new promising thermoelectrical material in the range of intermediate temperature, BiCuSeO attracts much attention due to the combination of low intrinsic thermal conductivity and relatively high Seebeck coefficient. In this study, the effects of substituting variable-valence rare-earth element Eu for Bi site on the microstructure and thermoelectric performance of BiCuSeO-based material were investigated. The results indicate that ions of two valence states, Eu²⁺ and Eu³⁺, coexist in the doped BiCuSeO samples. The doping of Eu not only improves the concentration of the carriers, but also modifies the band structure of BiCuSeO matrix, resulting in effective improvement of electrical transport properties. The electrical conductivity of Bi_0.85Eu_0.15CuSeO reaches 98 S·cm^-1 at 823 K, which is 6 times as high as that of the undoped sample. The power factor of 0.32 mW·m^-1·K^-2 and ZT of 0.49 can be achieved at 823 K for Bi_0.975Eu_0.025CuSeO sample. This study shows that the doping of variable-valence rare-earth elements can effectively improve the thermoelectric properties of BiCuSeO.

Key words: thermoelectric materials, BiCuSeO, variable-valence element doping

CLC Number:

O472

KANG Huijun,ZHANG Xiaoying,WANG Yanxia,LI Jianbo,YANG Xiong,LIU Daquan,YANG Zerong,WANG Tongmin. Effect of Rare-earth Variable-valence Element Eu doping on Thermoelectric Property of BiCuSeO[J]. Journal of Inorganic Materials, 2020, 35(9): 1041-1046.

Figures/Tables 10

Fig. 1 XRD patterns for Bi1-xEuxCuSeO samples

Table 1 Lattice parameters of Bi1-xEuxCuSeO samples

	a/nm	c/nm
BiCuSeO	0.39354	0.89413
Bi_0.975Eu_0.025CuSeO	0.39358	0.89423
Bi_0.925Eu_0.075CuSeO	0.39355	0.89436
Bi_0.85Eu_0.15CuSeO	0.39354	0.89442

Fig. 2 SEM images of the fracture surface of Bi1-xEuxCuSeO (a) x=0; (b) x=0.025; (c) x=0.075; (d) x=0.15

Table 1 Densities of Bi1-xEuxCuSeO bulk samples

Bi_1-_xEu_xCuSeO	x=0	x=0.025	x=0.075	x=0.15
Density/(g·cm^-3)	6.888	8.421	8.43	8.257
Relative density	77.3%	94.5%	94.6%	92.6%

Fig. 3 XPS (a) total survey and (b) spectra of valence state of Eu2+/Eu3+ for Bi0.975Eu0.025CuSeO sample

Fig. 4 Electronic bands and band gaps of Bi1-xEuxCuSeO (a) x=0; (b) x=0.025; (c) x=0.075; (d) x=0.15

Fig. 5 Carrier concentrations and mobilities of Bi1-xEuxCuSeO samples varied with x at room temperature

Fig. 6 Temperature dependence of electrical transport properties of Bi1-xEuxCuSeO samples (a) Electrical conductivity; (b) Seebeck coefficient; (c) Power factor

Fig. 7 Temperature dependence of thermal transport properties of Bi1-xEu1-xCuSeO samples (a) Total thermal conductivity; (b) Lattice thermal conductivity

Fig. 8 Temperature dependences for ZT of Bi1-xEuxCuSeO samples

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