A comparative study of thermoelectric properties in (Pr,Y)Ba₂Cu₃O₇ and PrBa₂Cu₃O₇–Ag percolative systems

Abstract

PACS 72. 74.25.Fy, 74.72.Bk Measurements of the temperature-dependent thermoelectric power S(T) and resistivity ρ(T) were performed to characterize two kinds of polycrystalline systems (Pr 1-x Y x )Ba 2 Cu 3 O 7 and Ag-doped PrBa 2 Cu 3 O 7 , each of which exhibits percolative behaviour at a certain doping level. At room temperature, Jonker plots of the thermoelectric power against logarithm of the conductivity in both systems show a similar tendency that two different fitting lines are intercrossed at the percolation thresholds. The ρ(T) behaviour below 100 K in each system with low dopant content obeys the variable-range-hopping conduction. Variations of S(T) in both systems could be reconciled with the Boson -Fermion theory based on the resonating-valence-bond model with reasonable dependences of fitting parameters upon doping.

Thermoelectric Properties in Transparent-Conductive Cerium-Doped In₂O₃ Films

“…(1) and (2), though ICO films are not exactly nondegenerated semiconductors. We have already reported that similar results are observable in thermoelectric properties of percolative oxide systems[15]. From the least squared fits (LSF) to the data (the solid lines), we obtain experimental values a = 228 and 282 µV/K for Eqs (1).…”

“…Results for the analyses of S(T ) data are displayed in Fig. 4(a) for the cases of Nd 2−y Ce y O 4 (NCCO) [14] and Ag-doped PrBa 2 Cu 3 O 7 (Pr-Ag) [15] which are known as electrondoped (n-type) and hole-doped (p-type) materials, respectively. In the former system, Ce was substituted for Nd in the atomic ratio y (at.%) while Ag was added in the volume fraction z (vol.%) in the latter one.…”

“…Overall features shown in Fig. 3(a) will remind us of the behaviors of S(T ) observed in metalsemiconductor percolation systems [15,18,19], for which cases a narrow conduction-band model [20] or a Boson-Fermion model [21] have been employed to explain the experimental data. In an attempt to interpret the present results, we propose a simple but useful tool for charactering thermoelectric properties in systems covering metallic and semiconducting natures.…”

“…Electrical properties including the resistivity ρ, carrier density n and Hall mobility µ were measured at room temperature by the van der Pauw method with electric current 5 µA and magnetic field 0.6 T. The optical transmittance was measured with a spectrophotometer in the wavelength range of 240-2600 nm. Measurements on S(T ) were carried out using a liq-N 2 cryostat in the range of 100 K ≤ T ≤ 300 K, by means of a differential method in a similar manner as in our previous reports [14,15]. The temperature difference across the film was kept to be a few K during the S(T ) measurements with copper-constantan thermocouples as sensors.…”