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Abstract:
The thermoelectric properties of the Magneli phase WO2.90 were
investigated, with special attention to how the thermoelectric
performance can be altered by changing its microstructure. Spark plasma
sintering (SPS) allowed the direct preparation of large amounts of
consolidated material. Adding Ta2O5 to the reaction mixture lead to the
formation of solid solutions W1-xTaxO2 90 via a concurrent reaction
between WO3 and Ta2O5 during the SPS treatment. In addition,
micron-sized inclusions containing tungsten surrounded by WOx embedded
in a WO2.90 matrix were formed, which act as additional scattering
centers. As a result, the thermal conductivity of the Ta-containing
samples was reduced by approximate to 30% over the temperature range
from 300 to 1100 K while the electronic properties remained unaffected,
which in turn enhanced the thermoelectric performance and led to a
relatively high zT value of 0.15 at 1100 K for n-type metal oxides.
