Formation of inhomogeneous micro-scale pores attributed ultralow κlat and concurrent enhancement of thermoelectric performance in p-type Bi0.5Sb1.5Te3 alloys

Selective Dissolution‐Derived Nanoporous Design of Impurity‐Free Bi2Te3 Alloys with High Thermoelectric Performance

“…In this respect, the creation of pores in thermoelectric materials can be an effective strategy to improve ZT because pores generate many interfaces at which phonons are scattered, even with negligible change in carrier concentration. [22] To generate pores in thermoelectric materials, several previously explored approaches include sublimation of impurities during sintering after intermixing with thermoelectric materials [23][24][25][26] and removal of tellurium from Te-rich Bi-Te phases. [27][28][29] Nagarjuna et al developed porous Bi 0.5 Sb 1.5 Te 3 alloys by sublimating polyvinylalcohol, which has a low melting point, from a composite containing Bi 0.5 Sb 1.5 Te 3 powder and polyvinylalcohol; a porosity of ≈10.6% was obtained, resulting in enhanced ZT at 400 K from 1.17 for the dense sample to 1.34 for the porous sample.…”

“…[27][28][29] Nagarjuna et al developed porous Bi 0.5 Sb 1.5 Te 3 alloys by sublimating polyvinylalcohol, which has a low melting point, from a composite containing Bi 0.5 Sb 1.5 Te 3 powder and polyvinylalcohol; a porosity of ≈10.6% was obtained, resulting in enhanced ZT at 400 K from 1.17 for the dense sample to 1.34 for the porous sample. [24] Shi et al reported the fabrication of porous Bi 0.5 Sb 1.5 Te 3 via 3D printing technology and achieved a large reduction in κ owing to the porous structure. [30] However, attempts to add impurities or tellurium for pore formation may leave the impurities in the thermoelectric materials and unintentionally affect the carrier concentration.…”

“…In this respect, the creation of pores in thermoelectric materials can be an effective strategy to improve ZT because pores generate many interfaces at which phonons are scattered, even with negligible change in carrier concentration. [ 22 ] To generate pores in thermoelectric materials, several previously explored approaches include sublimation of impurities during sintering after intermixing with thermoelectric materials [ 23–26 ] and removal of tellurium from Te‐rich Bi‐Te phases. [ 27–29 ] Nagarjuna et al.…”

“…In general, the size and distance of the pores generated in Bi 2 Te 3 ‐based alloys reported elsewhere are in the range of hundreds of nanometers to several micrometers. [ 24,31–34 ] These values are considerably larger than the phonon mean free path of Bi 2 Te 3 (one to tens of nanometers), [ 35–38 ] which is not suitable for enhancing phonon scattering. Therefore, a fabrication technology for impurity‐free nanoporous thermoelectric materials should be developed to effectively reduce κ L while ensuring negligible deterioration of their electrical transport properties.…”

Enhanced thermoelectric performance in Bi0.5Sb1.5Te3/SiC composites prepared by low-temperature liquid phase sintering

“…The decreased carrier concentration could be ascribed to strengthened carrier scattering at the pores induced by heat treatment. 44,46,53,54 Moreover, the intrinsic excitation temperature of samples heat-treated at 350℃ and 400℃ is shifted to around 360 K. The power factor of the samples heat-treated at 350℃ and 400℃ is much higher than that of the sample without heat treatment and 200℃ samples prior to the intrinsic excitation (as shown in Figure 1c). Figure 1d shows the temperature dependent thermal conductivities of heat-treated materials.…”