Abstract
Nanoporous architecture has long been predicted theoretically for its proficiency in suppressing thermal conduction, but less concerned as a practical approach for better thermoelectric materials hitherto probably due to its technical challenges. This article demonstrates a study on nanoporous PbSe–SiO2 composites fabricated by a facile method of mechanical alloying assisted by subsequent wet‐milling and then spark plasma sintering. Owing to the formation of random nanopores and additional interface scattering, the lattice thermal conductivity is limited to a value as low as 0.56 W m−1 K−1 at above 600 K, almost the same low level achieved by introducing nanoscale precipitates. Besides, the room‐temperature electrical transport is found to be dominated by the grain‐boundary potential barrier scattering, whose effect fades away with increasing temperatures. Consequently, a maximum ZT of 1.15 at 823 K is achieved in the PbSe + 0.7 vol% SiO2 composition with >20% increase in average ZT, indicating the great potential of nanoporous structuring toward high thermoelectric conversion efficiency.
Highlights
Introduction materialSecond, nanopores are likely more stable at high temperatures than the precipitates that are usually formed byWith the advent of efficient materials, thermoelectric (TE) annealing
A few methods were powerful strategy towards higher ZT is to lower lattice thermal reported on engineering the thermal transport of TE materials conductivity, in which various methods, such as nanostruc- by introducing nanoporous structures, such as altering the tural engineering,[2,3,4,5] alloying,[6,7,8] and constructing complex crystal structures[9,10] have using wet-chemical synthesis to prepare hollow structured prebeen utilized
We reported a systematic study on nanomaterials but has been more or less overlooked for a long time. porous PbSe–SiO2 TE composites, in which nanosized SiO2 particles were used to create randomly distributed nanopores
Summary
X-ray diffractions revealed no significant differences among the compositions of PbSe + x vol% SiO2, indicating no other than the PbSe matrix with Fm3 m symmetry, as depicted in Figure S1 (Supporting Information). For samples with SiO2 contents over 0.5 vol%, especially the 0.9 vol% one, the electrical conductivity deviated from the normally decreasing tendency near room-temperature (RT), showing a “bump” between 323 and 523 K Such an “abnormal” trend is ascribed to additional scattering processes, probably by grain boundaries or nanopores that involve energy barriers and exhibit different temperature dependence from the dominant acoustic phonon scattering. The boundary barrier is known as a thermally activated defect characterized with energy Eb, so its influence is fading away with increasing temperature Others, such as the composite effect, would retain its influence but with a smaller contribution (to the total mobility values) because of enhanced acoustic phonon scattering at higher temperatures. Promise of nanoporous structuring as an effective method to modify transport properties and improve the performances of TE materials
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