Thermoelectric power of proton conducting cerates

In order to gain further understanding of the protonic conductivity in the doped strontium and barium cerate ceramics, Sr/BaCe _1-xM_xO_3-δ, the thermoelectric power was investigated in the temperature range 500-1000°C in moist atmospheres. Plotted as a function of temperature the thermoelectric power values make an S-shaped curve. It is believed that this shows the transition from a low-temperature region dominated by protons to a high-temperature region with predominantly oxide ion and/or electron hole conductivity. The dependence of doping concentration on the SrCe _1-xY_xO_3-δ thermoelectric power was found to be small. In addition, the isotope effect on the thermoelectric power on substitution of H₂O with D₂O was investigated. The results show a notable difference when the sample was saturated with D₂O instead of H₂ O. Based on these results an attempt is made to determine the size of the contributions to the thermoelectric power from configurational and vibrational entropy, respectively