Ag‐YBCO compounds as thermoelectric material

Abstract

AbstractIn order to improve their thermoelectric properties, the transport properties of polycrystalline YBa2Cu3O7–δ (YBCO) perovskites were modified by partial substitutions of Cu by silver atoms and by submitting the samples to a thermal process at 600 °C. The Seebeck coefficient S (T), electrical resistivity ρ (T) and thermal conductivity κ (T) were measured in the temperature range between 77 K and 300 K. The Seebeck coefficient in all samples is positive in the measured temperature range and its magnitude increases with the Ag content from 30 μV/K to 130 μV/K. The behavior of the electrical resistivity changes from semiconducting to metallic as the Ag doping increases; its magnitude is always less than 0.9 mΩ cm. The thermal conductivity shows a weak linear temperature behavior and its magnitude decreases with Ag doping, which suggest that Ag atoms are efficient phonon‐scattering centers. In all samples κ (T) is less than 5 W/K m and in highly doped samples it reaches values close to 3.5 W/K m. From S (T), ρ (T) and κ (T) data the dimensionless thermoelectric figure of merit ZT (T) and the thermoelectric power factor PF(T) were calculated; these parameters reach maximum values close to 0.4 and 60 μW/K2cm, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)