Abstract
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.
Highlights
The phosphate glasses are semiconducting materials, transforming it as conductive materials that can offer more opportunities of applications
The performance of the thermoelectric material is measured with the figure of merit ZT = S2σT/κ or power factor PF = S2σ, where T is absolute temperature, S is Seebeck coefficient, σ is electrical conductivity and κ is thermal conductivity; the applications require ZT higher than 1
The Energy Dispersive X-ray (EDX) analysis showed a good purity in the composition of matrix
Summary
The phosphate glasses are semiconducting materials, transforming it as conductive materials that can offer more opportunities of applications. For these reason we decide to prepare composites from this glass due to their special properties. The performance of the thermoelectric material is measured with the figure of merit ZT = S2σT/κ or power factor PF = S2σ, where T is absolute temperature, S is Seebeck coefficient, σ is electrical conductivity and κ is thermal conductivity; the applications require ZT higher than 1. Several approaches have been proposed to increase the figure of merit These well-established approaches say traditional ones; the aim is to increase the power factor PF or reduce thermal conductivity by structural means to the atomic scale. The new approaches would promise a decoupling between electrical and thermal properties by using nanostructured materials that presented the related quantum effects at the nanoscale structures. The factor of merit obtained with thin layers (i.e. superlattices) is about 2.5 [2] [5]
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