Abstract
In order to improve their thermoelectric properties, the transport properties of polycrystalline YBa~2~Cu~3~O~7–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/K^2^cm, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)