• microwave sintering of bi2te3- and pbte-based alloys: structure and thermoelectric properties

    جزئیات بیشتر مقاله
    • تاریخ ارائه: 1392/07/24
    • تاریخ انتشار در تی پی بین: 1392/07/24
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     microwave sintering is well known as an expeditious process in applications involving ceramics and biomaterials. for powders in the nanometer range, rapid microwave heating could reduce material exposure to elevated temperatures, thus preserving nanostructures in the resulting materials. to investigate the potential of this technique for thermoelectric (te) materials, we have prepared samples of bismuth-telluride- and lead-telluride-based alloys from powders, for both materials, having sizes of partially agglomerated particles distributed from 0.15 μm to 7 μm. sintering of the cold-pressed powders was carried out in a microwave furnace for 900 s at temperatures in the range of 583 k to 623 k for bismuth telluride and 793 k to 813 k for lead telluride specimens. for optimized sintering times and temperatures, the samples obtained showed relative densities of almost 95%. scanning electron microscopy shows some residual porosity and a reduction of grain size, up to a factor of 5 for pbte, compared with optimized hot-extruded specimens. for bismuth telluride samples, the te performance in the range of 300 k to 460 k is poor, which is attributed to the arbitrary texture obtained from cold pressing of a highly anisotropic alloy prior to its sintering. in contrast, pbte exhibits isotropic properties, hence deficiency of texturing is not expected to have a negative impact on its te properties. harman measurements show a value of zt = 0.42 at 617 k for pbte p-type sintered samples, which is comparable to hot-extruded alloys from similar powders. the present work demonstrates that microwave sintering is a promising alternative to other powder consolidation techniques for polycrystalline materials exhibiting isotropic te properties.

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