The overall purpose
of the present study is basically to understand the manifestation of the thermo-electrical
properties of the matrix ZnO-P2O5 first, and of the ZnO-P2O5 composites loaded with different volume fractions of nickel (Ni) as conductive
fillers. In the matrix ZnO-P2O5, the values of electrical conductivity varied between 1.14 × 10-8 and 7.8 × 10-7 (S/cm), and the Seebeck coefficient value
varied between minimal value 265 and maximal value 670 (μV/K) in the studied temperature.
In composite ZnO-P2O5/Ni, it was shown that the Seebeck
coefficient changed from high positive to negative values when the filler
amount was increased, indicating a non-conducting to conducting phase transition. Such behavior exhibits that this transition
is accompanied by the passing of carrier charge from p to n type. The
study of thermoelectrically transport for high volume fraction of filler
enabled the achievement, for the first time on this kind of composites, of an
original transition called PTC transition. Thus, highest values of power factor
(PF = S2 ≈ 2 ×
10-3 W·m-1·K-2 at
407 K) were obtained, giving a possibility of industrial applications.
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