New Composites of ZnO-P2O5/Ni Having PTC Transitions and High Seebeck Coefficients

Abstract : In this article, we report the electrical conductivity (σ) and Seebeck coefficient (S) of ZnO-P2O5 matrix filled with conductive powder of nickel (Ni). The variation of σ versus volume fraction of Ni showed a non-conducting to conducting phase transition at percolation threshold (28 vol. %). The change of S from high positive to negative values exhibits that this transition is accompanied by the passing of carrier charge from p to n type. On the other hand, the measurements of σ and S as function of temperature, above the percolation threshold, showed a positive temperature coefficient (PTC) phase transition at Tc ≥ 400 K, linked with a high S = − 5000 μV/K, giving highest power factor PF = σ.S 2≈ 2.10− 4 W m− 1 K− 2. The temperature dependence of the volume expansion enabled to confirm that this transition is associated to the thermal volume variation in matrix. However, the temperature dependence of σ below the percolation threshold showed two different mechanisms: thermally activated hopping behavior at high temperatures and Mott's variable range hopping (VRH) at low temperatures.
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Soumis le : mercredi 22 janvier 2014 - 17:09:02
Dernière modification le : mercredi 14 février 2018 - 15:41:17

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A. Maaroufi, Omar Oabi, Bruno Lucas, A. El Amrani, Sébastien Degot. New Composites of ZnO-P2O5/Ni Having PTC Transitions and High Seebeck Coefficients. Journal of Non-Crystalline Solids, Elsevier, 2012, 358 (23), pp.3312-3317. ⟨10.1016/j.jnoncrysol.2012.09.003⟩. ⟨hal-00934895⟩

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