Thermoelectric figure of merit of oxygen-deficient YBCO perovskites

We have performed a study of temperature dependence of thermal conductivity κ(T)κ(T), Seebeck coefficient S(T)S(T) and electrical resistivity ρ(T)ρ(T) on oxygen-deficient polycrystalline YBa2Cu3O7-δ(0<δ<1) samples. The measurements of S(T)S(T), ρ(T)ρ(T) and κ(T)κ(T) were carried out as a function of oxygen content in the temperature range between 77 and 300 K, the influence of oxygen content on the transport properties and the dimensionless figure of merit (ZT  ) was studied. As the oxygen content is reducing the Seebeck coefficient and the electrical resistivity show a systematic increase while κ(T)κ(T) decreases. ZT(T)ZT(T) exhibits an enhancement reaching values close to 0.3 in the samples with low oxygen levels. This behavior suggests that the charge carrier density decreases while the oxygen level decreases and it opens the possibility to use this kind of materials as active thermoelements, which could work at room temperature and below it.