Thermoelectric response of oxygen nonstoichiometric YBaCo2O5+δ cobaltites synthesized via non-ion selective EDTA-citrate-metal complexing

The physical transport properties of layered 112-type YBaCo2O5+δ cobaltites, synthesized via non-ion selective EDTA-citrate-metal complexing, were systematically investigated by means of electrical and thermal conductivity as well as through thermopower measurements. The transport properties were shown to be markedly dependent on the oxygen content δ. The temperature dependence of the thermopower, S(T), exhibits p-type conductivity in the temperature range 60–320 K. In the low-temperature antiferromagnetic region, S(T) exhibits an unusual behavior (broad peak), which can be explained by the electron magnon scattering mechanism. The temperature dependence of the thermal conductivity exhibits a glass-like behavior, and no thermal conductivity peak can be seen at low temperatures for any of the samples. The absence of the phonon peak at low temperatures is associated with the oxygen nonstoichiometry, which brings about strong lattice disorder. The calculated figure of merit (ZT) shows values (∼10−5 at room temperature) too small for applications, as expected from 112-type cobaltite systems.