Difference between thermo- and pyroelectric Co- based RE-(= Nd, Y, Gd, Ce)-oxide composites measured by high-temperature gradient

Seebeck-Voltage measurements of Cobalt-based oxide-composites containing rare-earth elements (RE= Nd, Y, Gd, Ce) were performed under high temperature gradients up to 700 K. Several dependences were measured, Seebeeck voltage as a function of time U_S(t)or temperature difference U_S(Delta_T), closed circuited electric current as a function of Seebeck voltage I_S(U_S), or time I_S(t). While Nd2O3+CoO and Y2O3+CoO show linear n-type US(t)-behavior as usual thermoelectrics, Gd2O3+CoO possesses a large hysteresis. At both, Gd2O3- and Ce2O3+CoO also large time dependence I(t) referred to as pyroelectric material with high capacity were detected. Both anomalies became smaller when Fe2O3 is added or appear in Nd2O3+CoO and Y2O3+CoO when Al2O3 is added and can be explained by electron sucking into interfacial space charge regions, a new materials science challenge.