Electrical conduction and mass transport properties of SrZr _0.99Fe_0.01O_3-δ

The electrical conductivity of SrZr_0.99Fe_0.01O _3-δ was evaluated by a four-probe ac technique. The measurements were conducted in hydrogen and in oxygen containing atmospheres at 823 ≤T/K≤ 1273. It was found from the X-ray absorption spectroscopic measurements that Fe in the oxide is trivalent both in hydrogen and in oxygen. In order to determine the major carrier in the oxide, gas partial pressure dependences and isotope effect of hydrogen and deuteron on the electrical conductivity was investigated. In humidified hydrogen, it was found that proton conduction is predominant in the lower temperature region while oxide ion conduction starts to contribute to the total by increasing temperature of above 1173K. In oxygen containing gas, the protonic conduction is found to be predominant at lower temperatures while the contribution of the electron hole conduction is significant at higher temperatures. Hydrogen evolution property was evaluated using the SrZr_0.99Fe_0.01O _3-δ disc as a solid electrolyte. Hydrogen evolution rate obeyed the Faraday's law in humidified hydrogen at 1173K, suggesting that the transport number of ionic species is unity.