Low-temperature thermoelectric properties of Bi85Sb15−xNbx alloys prepared by high-press sintering

Enhanced thermoelectric properties of hydrothermally synthesized Bi0.88−xZnxSb0.12 nanoalloys below the semiconductor–semimetal transition temperature

“…48 For comparison with other similar bismuth antimony alloy systems, a maximum value of zT z 0.23 was attained for Sn-doped (Bi 85 Sb 15 ) 1Àx Sn x with x ¼ 0.00 fabricated using pressureless sintering techniques; 49 a maximum value of zT z 0.26 was attained at 260 K for (Bi 85 -Sb 15 ) 1Àx Pb x with x ¼ 0.00 fabricated using mechanical alloying in combination with pressureless sintering. 50 For Bi 85 Sb 13 Nb 2 fabricated using high-press sintering, a maximum of zT ¼ 0.36 was attained at 200 K. 40 It should be noted that zT > 1 could be attained for Bi-Sb-Te alloys around room temperature. 51,52 The downturn temperature dependence of the electrical conductivity around room temperature is attributed to semiconductor-semimetal transition, which is observed for all the alloys except the x ¼ 0.15 alloy sintered at 170 C. For the effects of Zn doping, the power factors are enhanced for all Bi 0.88Àx -Zn x Sb 0.12 alloys, except that for the x ¼ 0.15 alloy.…”

“…Besides, the thermopowers of all the samples only show small differences and display similar temperature dependence between 275 K and 425 K. Among the set of alloys sintered at 250 C, the x ¼ 0.05 alloy exhibits the largest absolute thermopowers between 75 and 375 K. It is noted that the variation of thermopower with temperature for the x ¼ 0.15 alloy is slower than other alloys, which resembles that of Bi 0.85 Sb 0.15 fabricated using mechanical alloying combined with high-pressure sintering. 40 Fig . 8 shows the thermoelectric power factor (sa 2 ) of Bi 0.88Àx -Zn x Sb 0.12 alloys with x ¼ 0.00, 0.05, 0.10, and 0.15 as a function of temperature from 50 K to 425 K. It can be readily seen that the set of alloys sintered at 250 C (Fig.…”

“…Besides, the thermopowers of all the samples only show small differences and display similar temperature dependence between 275 K and 425 K. Among the set of alloys sintered at 250 °C, the x = 0.05 alloy exhibits the largest absolute thermopowers between 75 and 375 K. It is noted that the variation of thermopower with temperature for the x = 0.15 alloy is slower than other alloys, which resembles that of Bi 0.85 Sb 0.15 fabricated using mechanical alloying combined with high-pressure sintering. 40 …”

“…38,39 The temperature dependence of the electrical conductivity for the x ¼ 0.15 alloy is similar to that of Bi 0.85 Sb 0.15 fabricated using mechanical alloying combined with high-pressure sintering procedure. 40 The temperature dependence of the electrical conductivity for Bi 0.88Àx Zn x Sb 0.12 is expected to be closely associated with the relative shiing of the T, L s , and L a bands. 41,42 The downturn of electrical conductivity above 300-325 K could be attributed to the semiconductor-semimetal transition, which will be discussed in the following section.…”

Thermoelectric properties of p-type Pb-doped Bi85Sb15−xPbx alloys at cryogenic temperatures

“…Moreover, previous results have shown that the thermoelectric properties of poly-crystalline Bi-Sb alloys can be improved by doping effect [20][21][22]. For example, it was reported that Bi-Sb alloys with Z value of 1.79 × 10 −3 K −1 at 196 K was obtained through partial substitution of Nb for Sb [23]. Bulk Bi 100−x Sb x exhibits an n-type semiconductor behavior when 7 < x < 22 or a semimetal character when x ≤ 7 and x ≥ 22 [24,25].…”