Effects of SiC Nanodispersion on the Thermoelectric Properties of p-Type and n-Type Bi2Te3-Based Alloys

Abstract

0.3 thermoelectric (TE) alloys containing a small amount (vol.% £5) of SiC nanoparticles were fabricated by mechanical alloying and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi 2 Te 3 -based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity (q) and Seebeck coefficient (a), but decreased the power factor of n-type materials by increasing both q and a. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi 2 Te 3 -based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of merit (ZT max ) of the p-type Bi 0.5 Sb 1.5 Te 3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case of n-type Bi 2 Te 2.7 Se 0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability and device reliability.

Spark plasma sintered bismuth telluride-based thermoelectric materials incorporating dispersed boron carbide

“…66 [23] 90 [12] More typically 1.1 (∥) and 0.8 (⊥) [7,9] Best room temperature values of up to 1.1 (⊥) and 0.8 (∥) quoted [7], typical value 0.9 (⊥) [16,19]. Note: max zT occurs ⊥ , the opposite of directionally solidified material…”

“…Mechanical property improvement has been the justification for the development of polycrystalline materials produced by a variety of processes including hot-pressing [11,12], extrusion [8,13], plasma activated sintering [14,15] and spark plasma sintering (SPS) [7,[16][17][18][19][20][21][22][23][24]. The addition of nanoscale particulate reinforcements (SiC [17,18,23], C 60 [7], multi-wall carbon nanotubes [12] and Al 2 O 3 [22]) have been pursued. The intention is to maintain thermoelectric performance in polycrystalline materials while improving their mechanical properties.…”

“…This effect has been attributed to preferential alignment of the basal poles with the pressing direction [7]. The addition of a dispersed nanoscale particle phase may increase the zT relative to a control polycrystalline specimen providing the volume fraction is optimised, largely due to reduced thermal conductivity [18,22,23].…”

“…The single-edge V-notched beam (SEVNB) fracture toughness test method was selected in preference to the indentation fracture toughness method, since the latter has been found to be unreliable [26]. [14] 113 HV0.01 100 HV0.025 [14] 56 -65 HV [8] 45 -64 HV [19] 55 -57 HV [24] 63 HV0.5 [18] 83 HV1 [23] 74 -80 HV0.5 [18] 87 HV1 [23] Flexural strength…”

“…[17,18,22,23] to allow comparison. The powders were ball milled in stainless steel pots with stainless steel balls at 350rpm for 10 hours in a planetary ball mill (QM-3SP2, Nanjing University Instrument Plant, China).…”