Thermoelectric power due to variable-range hopping

Polymer-Derived Silicon Oxycarbide Ceramics as Promising Next-Generation Sustainable Thermoelectrics

“…Interestingly, pure SiOC (C3) showed simultaneous increase in both S and σ with increase in temperature. Previous studies have shown such anomalous behavior for materials that exhibit electrical conduction mainly due to hopping of charge carriers . Our literature review showed that for amorphous materials, the ratio of S to temperature (T) is observed to exhibit a linear relationship with T –1/4 , a trend that was also observed in our study, albeit with some error (Figures c, d).…”

“…Previous studies have shown such anomalous behavior for materials that exhibit electrical conduction mainly due to hopping of charge carriers . Our literature review showed that for amorphous materials, the ratio of S to temperature (T) is observed to exhibit a linear relationship with T –1/4 , a trend that was also observed in our study, albeit with some error (Figures c, d). These findings further confirm that electrical conduction in our study was mainly via hopping conduction.…”

Tailoring the thermoelectric and structural properties of Cu–Sn based thiospinel compounds [CuM1+xSn1−xS4 (M = Ti, V, Cr, Co)]

“…The CuCo0.5Sn1.5S4 thiospinel compound with such temperature-dependent tendencies for σ and |S| (and their poor σ values), is close to that of two-dimensional (2D) Mott's variable range hopping (VRH) systems such as disordered anisotropic materials. 35,[76][77][78][79][80] Though the values of S are considerable, relatively low σ has resulted in lower power factor (PF = S 2 σ) in this CuCo0.5Sn1.5S4 compound, as shown in Figure 5c. PF increases with temperature to reach ~0.3 x 10 -4 W/m.K 2 at 673 K, but it is almost an order of magnitude lower than other such similar n-type thiospinel compounds like CuTi2S4.…”

Unified thermopower in the variable range hopping regime

“…It seems indeed, that this one is ill adapted in its present form to support the experimental measurements of the Seebeck coefficient carried out on different VRH systems. A simple illustration of this is its persistent disobedience during more than 3 decades, to the predicted theoretical laws [4]- [8], observed in most amorphous semiconductors [6], [8], [13]- [17].…”

“…Such a theoretical insufficiency of the TEP is attributed in this work to the fragility of the original hypothesis concerning the nature of the density of states (DOS), with which the evaluation of the Seebeck coefficient has been made. By reconsidering the hypothesis of the "slow linear variation of the DOS" near Fermi level on which most of the VRH theories of the TEP are rested [4]- [8], we investigate by using the percolation theory both conductivity and thermoelectric power when the DOS takes the asymmetric generalized form:…”