A high thermoelectric figure of merit ZT > 1 in Ba heavily doped BiCuSeO oxyselenides

Abstract

BiCuSeO system is achieved via heavily doping with Ba and refining grain sizes (200-400 nm), which is higher than any thermoelectric oxide. Excellent thermal and chemical stabilities up to 923 K and high thermoelectric performance confirm that the BiCuSeO system is promising for thermoelectric power generation applications.The thermoelectric (TE) energy conversion technology, which can be used to convert wasted heat into electricity, has received much attention in the past decade. The efficiency of TE devices is characterized by the dimensionless figure of merit, ZT ¼ (S 2 s/k)T, where S, s, k, and T are the Seebeck coefficient, the electrical conductivity, the thermal conductivity, and the absolute temperature, respectively. Until now, several classes of bulk materials with high ZT values have been discovered, 1,2 including nanostructured BiSbTe alloys, 3 filled skutterudites, 4 zinc antimonide, 5 AgPb 18+x SbTe 20 , 6 Tl doped PbTe 7 or (AgSbTe 2 ) 1Àx (GeTe) x alloys, 8 but they lack thermal and chemical stabilities in air. Therefore, TE oxides are expected to play an important role in extensive applications for waste heat recovery, on the basis of their potential advantage over heavy metallic alloys of chemical and thermal robustness. To date, several families of oxides have been developed as promising TE materials. Typical TE oxides include Ca 2.8 Ag 0.15 Lu 0.05 Co 4 O 9+d

Promising Thermoelectric Bulk Materials with 2D Structures

“…[80] According to solid state physical principles, the ZT value for bulk mate rials with a single parabolic band (SPB) along a certain direc tion can be given as: [4] The timeline for thermoelectric bulk materials with 2D structures, showing data from a superlattice, [8] SnSe, [11,[19][20][21] Bi 2 Te 3 , [12,14,16,17,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] BiCuSeO, [12,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] Na x CoO 2 , [57,58] Ca 3 Co 4 O 9 , [5...…”

“…BiCuSeO also exhibits an intrinsically low thermal conduc tivity, although the power factor for pristine BiCuSeO is not that striking compared to state of the art TE materials [116][117][118][119] [44,46,55,114,115] and fitting curves from the single parabolic band model. Reproduced with permission.…”

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

“…20 Recently, we reported a quaternary BiCuSeO compound that exhibits very low thermal conductivity. [21][22][23][24][25] High ZT values were achieved using this system by optimizing the electrical transport properties. Specifically, electrical conductivity was increased by Sr doping, introducing Cu deficiencies and Ba heavy metal doping.…”

Understanding the electronic and phonon transport properties of a thermoelectric material BiCuSeO: a first-principles study

“…An effective way of searching good TE materials is to find materials with intrinsic low lattice thermal conductivity, such as CoSb 3 [1], AgSbTe 2 [2], and MgAgSb [3]. Recently, a new layered oxyselenide BiCuSeO with very small lattice thermal conductivity was proposed to be a potential TE material [4], and a large amount of efforts have been devoted to enhance its TE performance [5][6][7][8][9]. Over the past five years, the ZT value of BiCuSeO has been continuously increased from 0.76 to 1.5 by doping to enhance the power factor as well as nanostructuring to further reduce the lattice thermal conductivity.…”

“…As for the origin of the low lattice thermal conductivity, it was speculated that the lone pair electrons of Bi 3+ possibly lead to a more asymmetric electron density and stronger lattice vibration energy [10]. Apart from the intrinsic phonon-phonon interactions, the grain boundary and defect were also believed to be important 3 scattering mechanisms [6,9,10,14]. In the theoretical aspect, the electronic band structure of BiCuSeO was studied by performing first-principles calculations [15], which suggests that a mixture of heavy and light bands near the valence band edge can lead to a relatively higher Seebeck coefficient and a reasonable electrical conductivity.…”