Thermoelectric performance of Zn-substituted type-VIII clathrate Ba8Ga16Sn30 single crystals

Abstract

We have grown single-crystalline samples of Zn-substituted type-VIII clathrate Ba 8 Ga 16 Sn 30 with n-type carriers by Sn-flux method. The actual compositions of the single crystals were found to be described as Ba 8 Ga 15.8À2y Zn y Sn 30.2þy (y ¼ 0 $ 0.54), where the charge balance is well maintained. As y goes from 0 to 0.42, the resistivity at 300 K decreases from 5.3 to 3.0 mX cm gradually, but the effective mass is essentially constant at 1.2 $ 1.5m 0 , indicating intact band structure near the conduction band minima upon Zn substitution for Ga. At elevated temperatures, the ambipolar effect on the thermal conductivity becomes less pronounced upon Zn doping, and the dimensionless figure of merit ZT for y ¼ 0.07 and 0.42 remains at rather high values compared with the nondoped sample. V

Thermoelectric properties of type-VIII clathrate Ba8Ga16Sn30 doped with Cu

“…The ZT values for the n-type BGS were enhanced by partial substitution of Al or Zn for Ga in the framework [16,[19][20][21]. Especially, the ZT value of the Al substituted BGS was enhanced up to 1.2 at 500 K. Furthermore, doping with Cu in Ba 8 Ga 16Àx Cu x Sn 30 at a very low level x of 0.033 led to the highest ZT of 1.35 among the n-type substituted BGS samples [21].…”

“…It was attributed to the increase of the carrier mobility and suppression of the pronounced increase in j (T > 450 K), which arises from the bipolar effect. The ZT value has a maximum value of 1.35 at 540 K. The substitution of Sb for Sn in p-type BGS, however, caused no improvement in ZT, the maximum of which stayed around 1.0 at 480 K [15,16,20].…”

Enhanced thermoelectric performance of porous magnesium tin silicide prepared using pressure-less spark plasma sintering

“…23 By assuming that the lattice contribution Κ L becomes constant above 615 K and that the bipolar contribution Κ b can be neglected below 615 K, 18 the two contributions can be estimated as shown in Figure 7 (b). The bipolar contribution Κ b is typically very small below the intrinsic conduction region of materials.…”

Preparation and Thermoelectric Properties of Zn‐Doped Sn‐Based Type‐VIII Single‐Crystalline Clathrate via a Grey Sn‐Flux Method

“…For example, Figure shows a typical photo of the grown crystal sample with Zn content x = 1. The obtained sample exhibited 5mm size, and it is as large as that of Zn substituted samples grown by β ‐Sn flux method …”

“…For the quaternary Sn‐based type‐VIII clathrates Ba‐Ga‐Sn‐X(X = Cu, Al, Ge), the dimensionless figure of merit ZT is enhanced significantly; For example, the ZT of Cu‐doped Ba 8 Ga 16 Sn 30 with n ‐type carriers using Sn‐flux method is 1.35 at 540K . Recently, it was found that the ZT of single crystalline n ‐type Ba 8 Ga 16 Sn 30 sample via white Sn‐flux method was enhanced by Zn substitution . In general, the quaternary Sn‐based clathrates Ba‐Ga‐Sn‐X were prepared by the method of Sn‐flux, Ga‐flux, and double‐flux of Ga and Sn.…”